For many creators, precise follower counts and related metrics can literally determine their income—whether a company agrees to work with them, how much they can ask, and so on. Without such they might feel like a fashion model with their height listed by the agency as "potentially between 150cm and 190cm."
Zaps of course can serve as an interest proxy, but zaps can easily be gamed, and if Nostr catches on—which I believe it will—there will arise a whole zap-gaming industry. Get ready.
And creators earning from zaps alone isn't overly realistic. Zaps can be a very nice added source, but I'm pretty convinced that even in a zap-happy world the bulk of revenue for most creators of a certain type will remain sourced from more traditional sponsor deals.
Could it be Nostr is just not the right place for creators that need dependable metrics to attract the kinds of regular sponsorships that will keep them afloat? They'd best remain on YouTube or Instagram? Quite likely, and I don't doubt that a lot of people here on Nostr would be delighted for the whole lot of them (creators, influencers, personalities, whoever) to stay as far away as possible. But I still think it's something worth mulling over.