A contract is between parties. The governments role is to arbitrate in the case of disputes not to help craft the original document and ensure understanding.

Not in the case of this contract, because it also enables the parties to, for example, become eligible for government incentives to be married.

Isn't this a case of "an ounce of prevention is worth a pound of cure"?

Requiring both parties to prove they understand the contract is probably more cost-effective in terms of, well, cost - and time - than it is to actually go on to litigate things.

Perhaps, but it's simply not the way things have been done. For example, I cannot imagine a legal infrastructure that would allow people to understand Terms Of Service. And that is with everyone using their own language.