Do you think some people think they are worth too much?

Yes there are some out there with to low of a opinion of themselves and there are others with way to high of a opinion of themselves. They value themselves higher than they should.

Maybe.
But sometimes people assume this about someone who doesn't want to give them attention although they might not be like that generally.
There can be many reasons someone might not want to give a person attention.

Nah, not without knowing more about them. There can be lots of reasons behind their ways of acting.

maybe they're just shy

Ha! My mother in law. Now I need to write a story about this.

Those people could knock airplanes down they got there nose so high in the air.