I suspect nobody cares because it's not a problem. That bit of code you're moaning about will only be called once per namedtuple. It's unlikely to be a problem.
Guess who cares? The person you replied to... and it would've been really easy to figure that out, given that parent went all the way to look for implementation, isn't it?
Anyways. The reason I cared is because I was working on a Protobuf parser, where named tuple was supposed to play a key role: the message class. Imagine my disappointment when I started to run benchmarks.
But namedtuple makes classes, it does not instantiate them. If you're in a situation where your bottle neck is defining classes rather than instantiating them, then I would hope you can appreciate that this is an edge case.
