Sticky back plastic

Why is it that most first year homework (in the first week) is to cover your school book in sticky back plastic Don't schools realise that there is limited supply of this awful product at this time of year. I had been organised and bought some last week (knowing that it would be needed). However, as I am so bad at covering books with it, I ended up throwing quite a lot of it in the bin. This meant that we had none left for the books that came home today that needed covering. I went out in search for some and came home empty handed. This resulted in one very cross lady. I rummaged through some cupboards and managed to find a half used roll from two years ago when my son was in his first year. Luckily, we had enough to cover her books. No doubt, there'll be more books that need doing tomorrow night.