Think about how we got where we are with par.
Before machinery and watering greens were located by the lay of the land. Then with TOC as the dominant model we standardized on 18 hole courses. With this kind of background for laying out courses, you will find a certain percent fall into categories 68, 69, 70, 71, 72, 73, 74. Of those 70, 71, and 72 were probably the most common. What the actual par was depended on the land.
Now with machinery and irrigation many architects choose not to be dependent on the land. Since 73 and 74 are so rare, but bigger is better, they probably try to do 72.
It would be interesting to see what pars Jones, Jones, Jones, Fazio, Nicklaus, Palmer, etc. come up with vs. what pars Hanse, Doak, Coore and Crenshaw come up with. I suspect you will get quite different distributions.
This is why 72 can have bad connotations. It suggests the possibility of something forced upon the land.