Why you gots to be a s**tbag?

The story:

I heard it at a restaurant the other day when I was eating
lunch. I initially just dismissed it as typical hipster/indie rock
crap, but when it got to the refrain, their falsettos coupled with
the high ceilings / echo chamber effect of the restaurant
caused me to hear it this way, and I nearly spit my burrito out.
I Shazamed it for the song name and correct lyrics, and the
rest is history.