Like I said in the first post, I saw 10/13 stages come up in game one at one event (not a huge one either, 26 entrant), and I wasn't seeing every set played so it could have been more. The variety is real, and the differences between stages get pretty big (there is certainly no stage that is just swappable with Skyloft, and even stages like SV vs Town and City have different sizes and platform lay-outs that end up mattering more than you'd think). It's not just an immature game; we run 9 starter locals in Brawl which is an old game at this point, and I see all 9 get used for game one (FD and Castle Siege are a bit rarer than the others but do happen). You just have to look around the room and see that different players pursue different things.
Like in my personal 4 matches under 13 stages at that event, I ended up on Kongo I think half of the time because I apparently overvalue it (it actually worked pretty well for me!), but I didn't see Kongo picked game one for anyone else. The way the striking system allows both sides to expressively tilt the game toward their favored stages and you seem to always end up on a stage both sides legitimately like is what makes it such a cool system. Like if you just use 5 stages and pick 5 like FD/BF/SV/T&C/Lylat, I know I'll end up on a stage I think is kinda lame, but since I as a player strike FD/SV/T&C early most of the time, I'll get very different results out of 13 stages but also consistently one my opponent also likes since his least favorite stages will be struck early by him in the same way I'm striking my least favorites.
I also addressed the time. It doesn't add significant time; once you're striking anyway, striking from 5 stages versus 13 is a very trivial time difference. This has been our experience locally actually using larger strike lists; it just doesn't make a difference to time. Certainly removing a stock has a way bigger effect, like probably 100 times bigger, than how many starter stages you have (and tight TOing in which people who aren't where they're supposed to be when their sets are called get DQ'd saves radically more time than anything else, but that's another topic).