Profit might not be the point, but it is going to cost time and resources to run an instance. Unless the admin is just planning on paying for everyone’s ability to use Lemmy on their instance out of their own pocket, ads or subscriptions may be necessary. And depending on how much time and effort goes into keeping it up, it wouldn’t be unreasonable for them to want to make a profit on it so they feel like it’s worth the effort.

I’d hate for an instance to blow up in popularity only for the admin to decide it isn’t worth the time/effort/cost and shuts it down.