Seriously?! Are people this rude by nature?

So, here’s the backstory.
I’m a tutor at the local library every Wednesday, helping 3rd and 4th graders whose English isn’t so great because they grew up in Spanish-speaking homes.
So I’m working with a student, and this older woman whom I’ve never met decides to approach me.
She stares at my shaved head (how dare a girl shave her head!) and asks:
“Did you really do that to your hair intentionally?”
I’m kind of taken aback by this unsolicited rudeness but I answer, “Yeah, it was part of a fundraiser for cancer research that my school organized.”
She just gives me one of those smug grins and bluntly says “Well, you look like a boy,” just before walking away.
The student I was with went into a giggle fit for the next five minutes, then she started poking holes in the furniture. Lord…
SERIOUSLY?!
Why do people feel the need to approach others in such a rude, unsolicited way? Is this the way they were taught to behave? Are there outside influences that make them so bitter?