I think that, depending on your society -especially in the past-, certain types survive easier than others.
I'm sure you can imagine that NTP types which lean towards critical thinking wouldn't do great surviving in an dictatorship where critical thought is often rewarded with work camps / death. Assuming that all types were equal in amount at birth, you'd still get demographic variations depending on place, time and society.
Which I think is something someone in the thread tried to point out.
I see no reason for each type to be equally prevailent, ergo I see no reason for each type to be equally common.
Ofcourse, it goes the other way aswell. A society full of ESFJs will set the norm to be like them -an ESFJ-, which can reflect itself in celebrities, political figures (iff democracy), ...