Server costs for large instances are a thing, and I think it’s a good idea to have an incentive for people to keep hosting them
Can leave it up to each instance how they want to monetise. A lot of instances have donations setup already, could get a “premium” account to help the upkeep of the instance you’re on and get rid of the ads
Also if people really hate them adblock exists
In that case I imagine eventually most big instances will end up with ads sooner or later. Everyone’s hyped for the fediverse now but excitement will die down and instances that take any significant amount of processing power will likely need some way of monetising
Many users of that instance would probably relocate to the next best instance without ads.