Because you just don’t do that. Claiming 50p FFS.
I know if I’d tried that on the last business trip I was on, my feet wouldn’t have touched the ground. Everything I’d tried to claim would then have been looked into in minute detail. But then again, I work in the private sector and am ultimately responsible to shareholders.
This is the kind of attitude that leads to the great Gawne-ism “Well, we had some money left over and it had to be spent on something”.
The term “Treat the company’s money as if it was your own” means be careful, be frugal and don’t take the piss. Not “Wahey lads! Get the chequebook out and the shots in!”