^obviously they do, but not busting every single micros they see online. as i see it, police only take actions to arrest (bust) places like this is because:
A) too many complaints from near by residence that police were too annoyed by the calls which they'll have to something about it.
B) business in a micro makes big profits which the money flow in between ignores too much taxes, which, also includes using girls overseas who do not have working permits.(also implies to tax profit)
here are 2 examples i've seen:
1) this guy who have a small apartment with 2 bedrooms, who only have 1 or 2 girls the most, he did not have that much customer in and out, using girls that are mostly local(very occasionally have overseas girls), and he's been running the place for the past 4 years totally safe!
verdict: he's making profit, while not enough to let the government to check his taxes, and also not having too many people in/out which doesn't affect the neighbours.
2) another person i know started off the same route, after a year or so he moved into a big apartment with 4 - 5 rooms, having at least 6 - 7 girls who are local + overseas. not even 2 months, place busted!
verdict: similar as pinky, fits both reasons A + B i've mentioned above.