I don't think everyone on Nostr today is a power user and many people do have more than one client app installed. On iOS almost everybody has Primal and Damus. On Android, almost everybody has Amethyst and Primal. That is on top of the 0xChat, KeyChat, Fountain, Nostur, Coracle, Jumble, Habla.news, Yakihonne. These apps don't do the same thing people will have more than 10 apps in every phone for sure.