In our grandmother's day, a lot of those aphorisms were taken 'sorta' seriously....even when they didn't seem to pan out. THEN they would say: "The exception proves the rule."
(--the reply obviously, is: "thus, the more exceptions, the better the rule")

Bill D's theory that "it all averages out" is as good as any.

Let's face it...many people just like simplistic answers and explanations of life and nature. It provides something to feel knowledgeable about for folks who didn't have lots of formal education.

The most common one I can think of is the one about the weather...used almost everywhere... "If you don't like the weather around {your state's ...or city's ...name here}, just wait 30 minutes!"