security is a big reason to go local first in general (not necessarily with crdts but they are a strong option), less data over the wire to central servers, you can avoid even needing to know about user data if it stays on their device(s)

collaboration software benefits a lot from this approach because people can just use it and know it won’t get out of sync

Also, anything where you might need data offline at a specific moment. Like if the internet goes down but you still need the thing to show to the guy at the place, you’ll be glad if they used crdts because you’ll automatically have a copy

Also, cheapskates who don’t want to pay cloud bills