Search engine crawlers, aggregators, vertical markets crawlers and so on may give you visibility, are not so much, and are usually well-behaved (i.e. respect robots.txt, announce themselves with a consistent user agent, etc).

Security/vulnerability scans doesn't ask too much pages, at least existing ones, and usually come from few IPs from time to time.

But AI crawlers could be really a lot, try to get all your pages, and not always are respectful about robots.txt or your performance, u. And don't give you anything back. There may be exceptions, but the few you notice ends having a negative impact.