OK so serious question that I should probably have already known the answer to:
I noticed for the last 2 bands I’ve seen that the drummer’s kit is mic’d to the wazoo. Like between 7 and 10 microphones, pointed at each drum, each cymbal and some “overhead” flying mics.
Are these for recording or just for the house mix?
musicians are lazy and roadies need to be efficient, so you can rest assured that 99% of the time if a mic is set up on stage it's going to be used.
multiple mics are needed for drums for the live sound. the individual components of a drum kit need to be balanced - the snare is (relatively) too loud, the bass drum could needs a boost, the cymbals might need some EQ, etc. to get all those parts under control you need them separated so you can deal with them individually.
in addition, if they're recording the performance then yes, it'll be used for recording also. the best way to record a live show is to split every mic signal: one side/split goes to monitoring and front-of-house (AKA the PA), i.e. what always happens; while the second side/split goes to a multi-track recorder for later mixing, overdubbing, etc.
If just for the PA, do they really use 7+ channels and adjust each individually? That seems like overkill
yes, they adjust individually - during sound check. once they've got the drum set sounding good and balanced, ideally the sound tech(s) won't have to adjust the drum mics again save for a tweak here or there.
bonus content: those 7+ mics are typically mixed down to a sub-mix called a bus. so if the band is really hyped when they hit the stage and the drummer is bashing the drums much harder than he was during sound check (which is rather unprofessional), instead of adjusting 7+ faders the sound tech can simply pull down the drum bus which lowers all the drum mics at once, thus preserving the relative balance between the parts of the drum kit.
