That's on your delivery person not those who created the rule/law, if they are ignoring the law and it upset you like this report him/her for it. My postman is a stickler for getting signatures, I wish he wasn't, it's a pain in the @$$ having to be here for adult signature or having to go to the post office to get my package if I miss him.
My neighborhood is about to get a levee upgrade. Part of that process is for the planners to get archeological and environmental clearance. That means someone will come round and take core samples from everyone's lawn. Last week every house got a registered letter from the engineers requiring a signature. They were all out for delivery for 3 days, followed by a pink slip telling us to pick them up from the PO. Truth is it would have taken USPS delivery so long to stop at every house in the neighborhood that it wouldn't have been practical. As understaffed as they are they really might not be able to handle a large number of signature deliveries.
Like you say though, some individual posties will want to do it, some will look for an excuse not to.