Do you know why I think the "click" became standard? I stumbled on the answer one day when I sent the click track to a spectrum analyzer.
The click was completely flat across the entire spectrum! So if you're tracking bass, you'll still hear the higher freqs; if you're playing guitar you'll still hear the lower freqs, etc.
Anyway, I thought that was pretty interesting. I also think it's due to the fact that the click's attack is very quick, the sustain is short and there's little or no decay. it gets in, nails the "one" and gets out of the way.
I was just subbing with a band who used a washy hi-hat pattern as a click and the band was all over the place. The attack was slow so they heard it "late", then it got lost under all of the other instruments. It was a trainwreck.
Typically I prefer a woodblock or cowbell when tracking drums. Something solid like that, b/c a click can be pretty sterile and unpleasant when it's blaring in your headphones.