Personally, I don't get the point of making people do their last names. I do get that some people may choose inappropriate names on their jerseys. But at the end of the day, students are in their last year and just want a bit of fun or creativity. So even if they can express that through jersey names, it makes it so much valuable then just having last names, which in my opinion, is just way too boring and dull. Of course, teachers should make sure to veto suggestions which are offensive or inappropriate, but for the most part of it, some students do actually tend to come up with funny ones. Like I remember I had a mate whose name was Owen, and his name was "Owen did I ask" (probably spelled differently). Like that's something which isn't appropriate in the slightest but still funny to most people.