> Do you have anything constructive to say about the merits of the leave to renew policy itself?

I've discussed this thoroughly in sibling threads: forcing people to leave every once in a while is an extremely useful tool in ensuring that they are maintaining a residence and ties to their home country (where they agreed they would return.)

B-1/B-2 are the quintessential examples of visas requiring "leave to renew" - and note: these folks are granted no permission to work or remain in the United States.

> immigrants aren’t entitled to anything? (but you presumably are!)

I don't feel entitled to anything whatsoever in other countries. As a citizen of the United States, however, our law does indeed entitle me to things that foreign guests have zero expectation or entitlement to.