why

[emilywell]

"There a man there with a black mustache and a certain look in his eyes ,that made me wonder if he might not have something interesting to tell."
In this setence ,why does it use "not"? "I" want to know something interesting or not?

[blacknomi]

If a man has a neon green mustache, he might have something interesting to sell.

Emilywell, hope that helps.