Felt pressured to tip for laser hair removal?

I went to my second treatment for laser hair removal. It was fine until I was checking out with the receptionist. I have already paid for 3 treatments but I had to pay $5 for an extra area I was doing. All I had was a $20 so she took it and asked if I needed change. I said... yes? Then they didn't have change so I just said I would pay with card. She then said something about how I could leave my tip on the tip line. I have been to other places where they don't even allow tips for this service, and have read that it is not customary, so I was confused. It was kind of embarrassing as I was left wondering if my laser specialist had asked the receptionist to ask me. I did not leave a tip in the tip line (I wasn't sure how much to tip and I would also rather bring her some sort of gift/gift card on my final scheduled visit if they insist on being tipped for something I consider almost medical) and the receptionist seemed kind of annoyed. Do most people tip for this? Don't these people get paid a normal salary to do laser hair removal? My specialist used to be a waxer. then a gynecologist before this...so I figured it was tacky and maybe even insulting! Do most people give gifts? I left feeling so awkward that I probably wouldn't even go back if it were not for the fact that I had already payed for 3 visits! I should also add that I bought this package at a discounted price due to buying it through a groupon. Does getting a deal mean I am now expected to tip?