Well you could say same thing about the answers that Google displays on it's pages instead of search results! If you don't want these crawlers to index your content I am pretty sure you can disable via robots.txt just like Google.
I'd also argue that Google directing traffic to your website is a good alignment of incentives. ChatGPT spitting out answers derived from your work with nothing given back to you in return is not.
I can't seem to find anything on OpenAI's crawler agent, so I'm skeptical they're considering robots.txt at all.
(This is an active area of research, though, and version of GPT that could cite its sources is something people widely agree would be valuable.)