It really seems like 5E pushes the custom background for anyone who isn't extremely new to the game. Like, the ones listed are just examples, and you're supposed to use them as a template for making up your own.
Huh. I didn't get that sense at all. Instead, I got the impression that the DM would be well advised to add a number of new backgrounds, ideally some specifically tailored to his particular campaign, and then have the players choose from the available options (maybe with some further tweaking).
Otherwise, my gut feeling is that it would very quickly drop away from backgrounds having any sort of meaning, and instead devolving to an excuse to min-max those proficiencies. But YMMV, of course.