Not to defend Fahrenheit, it's a nonsense scale, however: As with most subjective scales the entire scale can be split into good and not good. The top part is good and the bottom part is not good. The middle of the top part is seen as average good.
So around 75 degrees would be perfect, which is close enough for something as subjective as temperature.
This is why in things like movie or game reviews a 7/10 is seen as average. Like it's good, in the good part, but right in the middle not anything special. A 5/10 or lower is seen as not good, not worth seeing, not worth your time etc. This works for reviews, grades, person attractiveness rating etc.
Fahrenheit is the best human-focused temperature scale. 0 is super cold, 100 is super hot, 50 is the line between short sleeve and long sleeve weather (assuming no wind). Anything outside these bounds, it simply isn't worth going outside. But then everyone at a latitude <|37|° will say "that's not that hot" and everyone at a latitude >|40|° will say "that's not that cold," so really it's the best Kansas-focused temperature scale
Interestingly if you take the middle of the freezing point (32F) and 100F, you do get a mildly warm 71. No this does not prove anything, yes I'll still say it.
Then if you average THAT with 50, you get 60.5... and you see all three numbers make a triangle. Illuminati confirmed.
50 is great for just a light jacket and jeans. You'll never get too hot, you won't get too cold. So, yeah, as long as you've got clothes on it's pretty perfect.
If I want to wear less clothes then 70 is a good bit better, but 50 is damn comfortable.