Ya learn somethin' new every day

I see a psychiatrist once a year in the hopes of averting another mental crisis like I endured in 2006. (Really hope to never, never do that again.)
So I'm forking out my $160 in the office on Wednesday. They don't have debit so I have the secretary run the card as a credit. When she prints out the receipt for me to sign I am taken to see there is a line for a tip.
A tip?
Okay, I know to tip the dog groomer, my hairdresser, the waiter, the pizza guy, and the doorman, but am I the only one who didn't know you were supposed to tip your psychiatrist?

For the record I didn't take advantage of this subtle and very discrete way of asking for even more of my hard earned and carefully budgeted money. But if compliments for Dr. P's fine skill in his area of expertise, attentive bedside manner, thorough knowledge of nutrition and medications, as well as his agreeable personality and maybe even some boyish good looks could be translated into money then I would be happy to cast in my coins to the proverbial psychiatrist tip jar on high.
Accolades to Dr. P.
Hope you get my tip.