Pull request culture is about enabling distributed collaboration, i.e. I don't have push permission to your repo and you don't have push permission to mine, but we can still collaborate by sending each other pull requests and sharing our work that way. It's all about collaboration while not trusting the other person with write access to your repo.

> It's all about collaboration while not trusting the other person with write access to your repo.

If I don't trust someone enough to grant write access to my repo, I certainly don't trust them enough to rubber stamp their pull requests.

Nor should you. You treat their pull requests just as you should any code review: you study them and decide whether to approve (accept) them or not.