i can understand to a point ,but i think i would feel pissed if i lost my number and got hauled off because of it
I don't see an alternative. You are issued with a number and you're obliged to wear it during the race. It's not a lot to ask, If they announced that it was OK to create your own, you know what would happen -- you'd get loads of people turning up with home-made numbers, whether they were legitimate or not.
If you can't wear your number, for whatever reason, it's too bad. You'll be able to start the race but not finish it, or claim a medal.
It doesn't matter if it's issued the day before, you still have plenty of time to lose a number! I heard of one runner who got off the coach on the morning of the race, and as the coach disappeared over the horizon, he realised that his number had fallen out, and was still on the coach. He had to pull out.