To prove who you are you need a driving license, or a passport, even if you are not planning on using either for their intended purposes. Both cost money, and if you don't spend extra money (which a lot of people may not have) to get a full driving license, require renewal fees.
Otherwise you need to have x number of documents from 1 list, and y number of documents from another. And hope that you've got them, or bad luck.
It's honestly a nightmare when you get older and places don't even accept a birth certificate and bills going online. A lot of places don't accept PDF printouts of bills too!