Hm... My 2013 NUC in fanless Akasa enclosure runs 24/7 on a 6W CPU, I recently looked at the options, and the 2019 6W offering changes little in performance. Yes, memory got faster, but that's it.
My passive-cooled desktop is also running a slightly trottled down 65W CPU.
So yes, there are people who choose there hardware by TDP.
When looking for a CPU for a server that sits in my living room, I went down the thought process of getting a low tdp. I don't have a quote, but I seem to remember coming to the conclusion that tdp is the max temp threshold, not the consistent power draw. If you have a computer idling I believe you won't see a difference in temp between cpus, but you will have the performance when you need it.
These days, a quiet, pwm fan with good thermal paste (and maybe some linux CPU throttling) more than achieves my needs for a "silent" pc 99% of the time.
I would love to be told my above assumptions are wrong if they are.
Yah-- one should look at performance within a given power envelope. Being able to dissipate more and then either end up with the fan running or the processor throttling back somewhat is good, IMO.
The worst bit is, AMD and Intel define TDP differently-- neither is the maximum power the processor can draw-- though Intel is far more optimistic.
My passive-cooled desktop is also running a slightly trottled down 65W CPU.
So yes, there are people who choose there hardware by TDP.