Why? If a UI works for people, why does it have to be changed? That seems to me to be at least part of the problem: software designers think things have to be changed, when it's really just that they want to change them, for whatever reason, and don't stop to think about the impact.
a lot people just don't like change
A lot of people have things that work perfectly well for them and don't like having to re-learn their workflow whenever some software designer has a bright idea. I'm one of them: I still run a KDE 3 desktop on Linux because it works for me and I don't like having my UI messed with just because somebody designed some new eye candy.
This how I feel about every version of Skype (for OS X) since version 2.8.x. The Skype UI had two windows - one for contacts and one for conversations. This made it easy to tuck Skype in a small corner of your screen. I think starting at version 5 they switched to one giant window and the community, pretty unanimously thought it was one of the worst UIs they had ever used (see this blog post: http://ignorethecode.net/blog/2011/03/30/skype_5/). The change seemed completely unnecessary and made things very non intuitive. If I myself had trouble using it, I think it must have been even worse for people who do not use computers so often. Indeed many people reverted back to 2.8. I used 2.8 up until a few months ago when Skype finally decided to drop video support for it.
I think the newest version of Skype does let you break things into new windows, but to me it seems that it should be the default.
My main point is: the UI was already great, it didn't need any changes.
I'm still using 2.8 - if the other side cares about video, we'll use a google hangout, but skype's never getting upgraded again. Man was that a disaster.
Because it's a web application. In the old days, you could use that old version of said software until your motherboard gave out 15 years later. However, today there is only ONE version of Gmail. Everyone has to use that version. Hence one person's "New Feature" will be another person's reason to cry. The cost of keeping X versions of Gmail in production is just too prohibitive.
If this is true, then to me it's a reason not to use web applications. (And I don't, for the most part; I still run KDE 3 on Linux, and use KMail to read email. The only web applications I use routinely are for things like paying bills, where I have no choice but to use the web UI for the bank or credit card company or whatever. And every so often those change and I have to re-learn things for no good reason.)
How much is the cost of updating the old interface once in a while when the backend API's change? They don't need to keep improving to versions in parallel, just keep the old one working is good enough.
There can be numerous of reasons why something 'has' to be changed. These changes are not always justified from some perspectives of course. If these perspectives represent the majority and also on the long run, something's wrong and perhaps that is your point. But sometimes, change is for the better, for the majority, especially on the long run. Often, with software design, you reach local optima, and to get further (more user friendly, more flexible, incorporating new or changed features, adapt changes in hardware, or things happening outside, etc), you'll need to move away from the sweet spot the majority settled with to get to another (hopefully better adjusted) local optimum.
Finding examples of cases where this did not work are no argument against all changes.
And as far as people not liking change. This is not only about re-learning. Change on itself is often met with tough resistance. And this resistance is often rationally hard to justify. Your example may or may not be like that (I don't have enough perspective to tell), but perhaps re-learning would have been more than compensated by the amount of time saved due to new features.
Of course this is always possible in general terms. But I was talking about a specific set of cases: redesigns of UIs that already work and that already have a huge base of existing users who will have to relearn what they know. In my experience, it's extremely rare for that kind of change to be "for the better".
you'll need to move away from the sweet spot the majority settled with to get to another (hopefully better adjusted) local optimum.
And in the process, you will have to move through a "pit" of UI suck where lots of people have significantly worse productivity for a significant period of time. And for what?
Finding examples of cases where this did not work are no argument against all changes.
I didn't argue against all changes; as noted above, I was talking specifically about software UI changes that force existing users to re-learn things for no good reason.
perhaps re-learning would have been more than compensated by the amount of time saved due to new features.
How much time saved? And how long before that savings pays back the huge cost of the switch, per the above?
And can these numbers even be measured anyway? Sure, Google can measure to the millisecond how long it takes for you to move the mouse from one place to another, and no doubt they have numbers to show that the new GMail UI shaves critical milliseconds off certain common operations. But can they measure the frustration caused by changes like this? Can they measure the emails that don't even get written because people get fed up with their new UI? Can they measure the cost of keeping people within their walled garden?
This problem is not limited to Google, of course; I think it's endemic in the software UI world. I think software UIs are like fashions: changes are largely driven not by functionality but by an arms race for users' attention.
Why? If a UI works for people, why does it have to be changed? That seems to me to be at least part of the problem: software designers think things have to be changed, when it's really just that they want to change them, for whatever reason, and don't stop to think about the impact.
a lot people just don't like change
A lot of people have things that work perfectly well for them and don't like having to re-learn their workflow whenever some software designer has a bright idea. I'm one of them: I still run a KDE 3 desktop on Linux because it works for me and I don't like having my UI messed with just because somebody designed some new eye candy.