Well there is that and there are users that post GPT SEO trash to Reddit et al, which is what the attestation API could help with.

the spammers are quite capable of buying several hundred old phones with valid attestation certificates to pump out crap

Which is orders of magnitude more expensive than deploying the bot to a cloud or botnet.

I don't know how much bot spam pays these days. Maybe it's still worth it.

the attestation requirement increases the cost but also increases the value of the spam as the spammers competitors are put out of business