Here's another stupid theory.
In the beginning, after the age of enlightenment, the Vulcans created the life of pure logic. It was awesome. However... How many decades were they going to get off on this before they noticed that no one was fucking and there were no children, ipso facto no new next generation?
The species was fucked.
An artificial widget had to be introduced to force these nerds to copulate.
Pon far is the ultimate countermeasure to the selfcockblock.