I think this thread answers that question 🙂. I reckon it just sounds scary to make your own QR code, especially if you don't particularly understand the process, so folks just search for someone to do it for them. This is how all those QR codes you see at restaurants and on signs work, it only needs to be generated once and then the image can be put anywhere on the internet or in meatspace (though they probably often use some kind of dynamic link for stats, too).

Hope this helps!