Isn’t that because there are regulations that say those provisions aren’t allowed (whether directly or indirectly)? The US doesn’t really have such laws.
It stems from fundamental difference in how civil law and common law think about contracts. In civil law, a contract is typically only valid to the extent both parties signed in good faith and have a similar understanding of the ins and outs. It's my understanding that in common law, contracts are essentially creating law.
>Surely you can’t stipulate just anything in a contract and have that upheld as binding by a court, even in the US?
That's a great question. I'd expect that courts would not uphold claims to one's first-born child[0][1], but only because that sort of thing is already illegal (human trafficking). As for stuff that isn't illegal, I expect that YMMV.
That said, people actually "agreed" to give up/assign their first-born children with these "Click-wrap" agreements.
That people are so cavalier about such things should be a huge red flag for regulators to require not just a link to such terms, but that both parties should be required to demonstrate their specific understanding of terms and conditions before such a contract can be considered enforceable.
But that's not how US courts have interpreted this sort of thing. So, as always, Caveat Emptor!