If people from Poland are called Poles, why aren't people from Holland called Holes?

Why don't they speak Hollandaise?

Why do croutons come in airtight packages?

And why don't they weigh 2,000 (or 2,200) pounds? They're really crougrams.

10. Why is a person who plays the piano called a pianist but a person who drives a race car not called a racist?

And why does a phlebotomist suck blood instead of phlegm?