[mauvehaus]

I have a weird address, and easily 30% of websites insist on fucking it up by applying validation rules that might make sense from 20,000 feet, but don't actually work in practice for our address.

The most straightforward of them is that some validation services insist that our ZIP code is for the next town over instead of the one we live in, which has its own post office. Nothing correct happens if our mail goes to the wrong post office because they (rightly) have no idea how to deliver mail to us.

I wouldn't be so confident that 100% of that 70% don't know their own address. For at least some of those cases, I'm willing to bet they know something you don't about the vagaries of mail and package delivery to their address.