If every time there was a metal theft in the neighbourhood the metal yards were visited, or the police spent time watching such places, I think it would have an effect. This stealing becomes rampant, because it is so easy and is never followed up. It must cost Malaysia millions of dollars a year as well. Not bad for a "small" theft.

But you are right — police are undermanned, and have to spend time doing useless stuff, like (here) checking cases of consenting adult sex, sale of sex toys, gay sex, etc etc.

It's the same everywhere unfortunately. 'Small' thefts are relegated to not worth worrying about and undermanned police forces – or police forces focussed on the 'big' crimes – have neither the time nor the resources to investigate. They tend to be regarded as victimless crimes too but, of course, they're not. There is often an impact on people as you have just experienced.