Tipping anyone is always optional.
It is something that people usually do though, just as with servers, nail care providers, and hairdressers.
I am a massage therapist and am tipped 99% of the time. I don't expect it, I NEVER would automatically add one on or suggest that people leave one. That being said, I usually am tipped 20% (minimum) and up.
"Yes! Live! Life's a banquet and most poor suckers are starving to death!" Auntie Mame