But is running your own instance worth anything? People use social media mainly to gather followers and likes. So there needs to be a reputation at play provided by the service provider to make sure those are real. Having a gazillion followers and a trillion likes on your own instance will not make you a celebrity.
Social media doesn't have to be about celebrity, or about promoting a personal brand. The big silos have promoted this use case because it aligns with their advertising incentives. But connecting with people with similar interests is another use case, as is keeping up with your friends and family.
I also think you misunderstand how following works on the Fediverse. My main account is on a small server with about 400 users, about 50 of which are active daily, I guess. But I have around 1000 followers, almost all of whom are on other instances (probably 20 or so are on my instance).
Posts to an individual mastodon server get shared across the network, people from other instances can "follow" your account (on your server) and their instance will subscribe to your posts. They can "like" or re-post your post (with or without a comment) to get your account (on your server) more visibility and possibly more followers. In that regard I think these ideas are present, but now there is more than one server.
This is only my opinion, but I think the gathering of followers and likes is something that the commercial product requires in order to keep people engaging with a product that they might otherwise put to the side.
I can see a celebrity or official or someone wanting to run their own instance to be the "canonical" or "verified" one, like, "This really is The Rock, because the instance is from TheRock.com, their website."
