It's kind of like after sex, you get up and wipe your dick off on the curtains. It is impolite.
They cut the animals throat and let it die by bleeding out instead of just shooting it in the head with a captive bolt for a clean kill.
Many consider it cruel as the animal takes a lot longer to die and suffers more vs. other kill methods.
You should see the one eye in my pants. It's fucking huge.