The average person just isn't tech savy enough to locally host. Its easy to tell people to just host stuff themselves but its a lot of added complexity and maintenance responsibility that most just don't want to deal with. I agree that it would be best if everyone just locally hosted all their services but we live in the real world where the average joe schmo is either too uneducated or busy with their life dramas to learn computer networking or just plain ol' lazy and indifferent to giving up personal privacy as long as they can change RGB lighting with a phone app they are happy as peaches.

That’s not the easy way, though. People go for home automation in the first place to make something easy. Getting some awful proprietary spyware doodad to work with HomeAssistant is usually not the “just works” experience they’re looking for.