I get asked this question from time to time.  My answer to the question is "because I'm old".  Maybe "old people" only comment on things that they know about is why they seem so savy.  I rarely go out on a limb and suppose.   It's probably a condition brought on by being proved wrong one too many times.

I wish that I was as smart as I thought I was when I was 20 years old.

I get philisophical when I'm drinking.  Ignore me at times like this.

Quoted: I've discovered that I'm at my smartest when drinking, but other people are at their dumbest when drinking. Odd.

Exactley!  Dude! You are brillaint!