He's using Gumroad (which I use as well). Gumroad turned on tipping as an opt-out feature for all sellers around one or two months ago. If you had a product you were already selling on Gumroad, like I was, the tipping feature was automatically enabled for the product and you have to go in and manually turn it off.

I felt the same way you do about tipping for an info product, but I left mine on and people do use it; turning it off would be turning down extra income.