Differences in instance-level topical focus and moderation philosophy, for one. Also physical location and “vibe”.
There are a certain set of bigoted and/or extremist instances that I would judge an instance for not defederating from. There’s a reason I’ve stuck with .world even through some turbulence. Some heinous shit shouldn’t be tolerated by anyone.
I only really wishlist games that haven’t come out yet that I’m interested in, to remind me to buy it when it comes out. Only about ten items on mine.