I actually know identical twins that do that... Seems quite common. One managed to board a plane with the ID card of the other one for instance.

I knew a guy who had a black-sheep-ish twin brother. He was starting to turn his life around, but then stole his brother's ID and did a bunch of shit. We were like, "wait why would he steal your ID--oh yea..duh...you're twins"

A friend of mine and his brothers once (allegedly) traveled around South America on a single driving license. They look sufficiently similar to the photo and I'm guessing they weren't checked often.