VPN providers and TOR exit nodes are a different beast, IMO. They're potentially liable for everything that goes through them, but it's a "push" model, not a "pull" one. Plenty of organizations don't want to interact with, or intermediate in hosting, TOR exit nodes, because they fear any kind of illegal thing could come through those nodes - but until something specific does come out, that's a risk management reason, not a legal reason.
In contrast, IPFS gateways are running on a "pull" model. Anyone can come to the gateway, and pull through it anything that's stored anywhere in the IPFS network. This is meaningfully different, in the same way "users could post illegal/infringing content to YouTube" is different from "there exist illegal/infringing content on YouTube already posted, available to anyone who know the ID to put in the URL". In the former case, possibility of "bad" upload doesn't create a problem until such upload actually happens; in the latter case, possibility of a "bad" download is a problem even if, so far, no one actually downloaded the "bad" thing.
> I think that's why DMCA safe harbor exists, and it could be argued that an IPFS gateway is acting as an OSP
I don't have any argument against that. I assume this wasn't tested in courts yet, and the rights holders are exploiting this uncertainty, expecting that no IPFS gateway operator will try to contest the DMCA claims.