At least for Nvidia and AMD desktop GPUs/cards, the priorities are:

#1 (by far) "can it play [hot game of the moment] in 4K?"

#2 (maybe) "is the fan noisy in desktop mode?"

#3 (for nerds) "can I run LLMs on it?"

I don't think top efficiency in desktop mode is on anyone's list, and even if it were, it would be hard to come up with a design that uses hundreds of watts when running top-tier games or LLMs, but also uses as little as possible when idle?

No, rather that they focused on peak performance, i.e., "churn out the most raw throughput at 400W+", rather than "get as close as possible to 0W when idle or in common uses".

Very different metrics - the former is about optimizing your architecture for pushing the most operations, the latter is about being able to power as many things off as possible.