I can’t speak for the UK, but some
TSA agents in the US are stealing from luggage. If theft wasn’t so rampant, we would all be okay to leave valuables in our checked luggage, but no frequent fliers will do this, as there is a mistrust in the system overall…

Petty theft isn’t really chased after or prosecuted in the US, and hence petty theft is rampant in the US as minimal consequences if any. Unless they are made an example of, but this is the exception.

The airport system is rife to be targeted by organized crime such as bulk money, drug, or gold delivery stealing; we are talking millions of dollars versus petty theft. Most petty theft we don’t hear about….and is probably more prevalent than what we are led to believe….