People are often reluctant to execute UI to permanently remember choices because they want to preserve the option to choose in the future.
For example, say I have a workable command of French, but want the ability to translate French in the future in case I don't understand a particular paragraph. So I put up with the annoying dialog over and over because I'm afraid to not have it when I want it.
Always/never UI is almost always a design failure IMO.
Another example is the intent chooser in Android. I put up with the dialog that asks whether I want to use Gallery or G+ photos because I fear not being able to choose in the future when I have some other viewer I want to use, or when there is some particular feature of G+ that I learn about and want to use.
In many cases this isn't rational if you think it through. There is probably some UI to reset the intent option somewhere, and finding it then is probably less time overall than dealing with this dialog over and over. But you don't think that through in the moment, you get slightly frustrated, press "not now" again, and get on with whatever you were trying to do.
You can always re-enable the translation popup through the page's context menu. It has an entry for "Translate to English" (or whatever your preferred language is) right there.
The problem is that a "permanent" decision has to be made before the user has the option to discover how to make it less permanent.
When it comes to UI issues, the existence of a solution with enough poking around is rarely a solution at all. The problem is that the UI is creating a conflict for the user at the beginning; being able to resolve a conflict is far worse than never creating the conflict at all.
For example, say I have a workable command of French, but want the ability to translate French in the future in case I don't understand a particular paragraph. So I put up with the annoying dialog over and over because I'm afraid to not have it when I want it.
Always/never UI is almost always a design failure IMO.
Another example is the intent chooser in Android. I put up with the dialog that asks whether I want to use Gallery or G+ photos because I fear not being able to choose in the future when I have some other viewer I want to use, or when there is some particular feature of G+ that I learn about and want to use.
In many cases this isn't rational if you think it through. There is probably some UI to reset the intent option somewhere, and finding it then is probably less time overall than dealing with this dialog over and over. But you don't think that through in the moment, you get slightly frustrated, press "not now" again, and get on with whatever you were trying to do.