Contrary to the sibling commenters, I found this pretty tricky to do; I was always too close to the curb or the lane marker, I lost my natural sense of where my car was positioned on the road. I have the same general surprise that you can just use a US license to drive in Europe --- but you can. The IDP seems pretty silly, especially knowing what little it takes to pick one up.

You could certainly question the wisdom of allowing short-term foreign visitors to drive on their foreign licenses, but taking that policy decision as a given the IDP is a reasonable implementation of it (even if I suspect its main function is to attach a fraud penalty to the "Prawo Jazdy" wheeze). Maybe something akin to the machine-readable passport code would be an improvement, but considering how long the likes of Real ID adoption have taken and that the IDP system isn't particularly broken, I can see why that wouldn't be prioritised.