That's exactly what I get, when I tip at the buffet breakfast. It goes far beyond than clearing my plates.
I do not tip systematically and, at some hotels, like the Aloft, I never left a tip, as the treatment that I receive is just the ordinary service. Another place would be the main restaurant at the ROSH.

But, as you indicated, we have been off topic for a while. I just wanted to clear up that idea that leaving a tip, when you feel that the staff has been good to you and attentive to your needs, was 'weird'.
Once more, there should be no pressure either way; do whatever you feel is appropriate, according to the way you have personally been treated.