The reason why multi-discs became frowned upon was because it made the CD cases larger. Personally, I didn't mind changing the disc once or twice or even 4 times, when playing, because there was a lengthy period between changes.
As disc-media matured and programming languages and compression techniques improved, companies started being able to fit all their games on one disc, and touted it as a feature. But now, gamers almost EXPECT a game to fit all on one disc, meaning that developers have this bizarre notion that their games HAVE to fit on a single disc. This means that a developer will start to cut things and take short cuts in order to fit everything on one DVD or Blu-ray disc.
And that's sad. Developers should not fear having to put things on multiple discs. I would hate it if a game didn't turn out as good as it could, all because they had to cut things to fit it on one disc. Seriously, changing discs is not difficult. Just open the tray, pop the disc in, close the tray. Takes all of 10 seconds, probably not even that.