> so why should you care?

Because you don't have the item you ordered until a second is sent?

I was under the impression that because I've told UPS that they can leave packages without requiring a signature, I'm liable for packages that disappear. But I'm not sure - I have never had a package stolen, so I don't know what would happen

Because some thief is getting away with it.

... and now associates your name and address with items of value to be had.