system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: With all the anti-union rhetoric we hear in the US why are the police unions never targeted by politicians and interest groups.
gpt
1) Police unions tend to wield a lot of political power.  There are something like 35,000 cops in New York city, which is high for most municipalities, but on top of that being a sizeable voting bloc, a LOT of people are friends of, family with, or married to police officers, which grows the strength of the bloc a bit. 

2) Going after the police unions, much like trying to cut the size of the military, is seen as anti-American.  The police do thankless jobs, and there are people that support the heck out of them, so if you alienate the cops themselves, you also alienate a LOT of those who support the cops that are out there keeping them safe from harm.  There's also concern that if you hurt their union, you're hurting their ability to do their jobs, and crime will rise. 

3) Cops and politicians are "on the same team".  In addition to whatever their core job is, cops are also the enforcement arm of the legislature / mayor / governor / whoever.  If the legislature and governor enact a law that outlaws firearms, the cops are the ones who have to put their lives on the line to actually enforce that law, so it demands a peaceful coexistence.  This is also the reason that cops tend to look after other state officials and vice versa.  They're all a part of the same engine, and the engine doesn't work if a piece of it gets thrown out of whack.