Yep. The issue is that separating Notifications and maybe even DM conversations between apps can get quite complicated. Imagine talking shit about life with your gaming friends and then load all those DMs in your work app later on. Same for family chats and tiktok chats.. It feels very off. There is a different level of trust/security in the user's mindset when using separate apps.
Discussion
In that sense, I’m inclined to think people may opt to have different “subkeys” if possible for different usecases.
Right now in my case, I have different npubs for DoShitters than for my personal npub where I post and follow different kind of stuff, but I love that with both of my “identities” I can surf in all the clients I wish.