The ink! Easy to forget in our digital world. I would have thought that longer extenders would enhance legibility at small sizes, to distinguish characters better. But, I guess it could make the textblock look spotty or cluttered. I bet there's a book with these answers...
I was actually looking at using Lapture for a project the other day. Maybe now I have to pick up that book and use the caption size at display sizes.
It's always tricky to tell if something is because "it looked better" or if there's a deeper meaning or convention I'm unaware of. Thanks for your responses Florian! I think I'll stick around and learn some things