Why does the \$ Q\$-factor depend on the resonant frequency?
So why a higher resonant frequency implies a higher Q-factor, which is supposed to measure how sharp the frequency response of our resonant circuit is?


It measures how sharp the resonance is, relative to the resonance frequency. 

This might make resonant circuit topologies or designs easier to compare for certain purposes if they're designed at different resonant frequencies.

If you want a measure of how sharp the resonance is that isn't dependent on the center frequency, you can always just use \$\Delta\omega\$.