Quite so. Immigration have a 'secure' database of every foreigner entering and leaving the country, including pictures and fingerprints. Most tourists will be staying in hotels where the hotel must report who is staying to the police. I know some long term folks have condo, houses etc, but they must send a 90 day report in? So the police only have to after the real criminals, those that are on overstay, dealing drugs etc. Presumably these kind of folks dont frequent discos, they keep their head down.
Raiding these places full of foreigners on the off chance of catching someone is over the top. They should do some detective work instead, then if they get a tip off that a particular venue has some criminals, fair enough, raid it, but just randomly raiding bars, discos etc doesn't work well and upsets the real tourists.