I think you're missing out on an important point - Users are not the same as Customers.
Customers pay you money, they are what you need to build a business. Having millions of users who don't provide any revenue is only useful if your goal is just to be bought by someone else.
I personally think that it's a sad state of affairs that most startups don't seem to be interested in building businesses, but instead just want to play the acquisition lottery instead.
For many startups users are also customers because they pay in one form or another for the startups services. Of course there are a few startups that have enough funding to not care about monetization at all but thats an exception imo. I see much more web app service startups, mobile Apps, Games etc that actually charge something even if its not upfront.
I run a games startup and our users are customers as well.
Customers pay you money, they are what you need to build a business. Having millions of users who don't provide any revenue is only useful if your goal is just to be bought by someone else.
I personally think that it's a sad state of affairs that most startups don't seem to be interested in building businesses, but instead just want to play the acquisition lottery instead.