Because when there is more plants, that is a bigger risk.

There are some people who are running 4000W of lighting in there grow area, then there are smarter people who choose to run only 150W or 400W, so who do you think is more at risk?

Big time growers also get more cocky with each grow. They figured, "hey, I got away with running a 1000W lighting system, lets do 2000W next time" and with each grow, they increase plant production and light production until, eventually, they run so much power that the electric companies are like, "WOW! $500 a month on power alone, we'd better investigate" and bango! Busted.

There are smart growers and there are dumb growers. The dumb ones run thousands of watts in their own home, tell their friends, and show it off. Then the smart growers who run much smaller amounts of lights that are not detectable, or, don't cause any sttention, who don't tell anybody, and don't show it off.