Alright. I'm gonna wade into this one....
I'm not a rider, so I can't speak from firsthand experience as regards to the discomfort of a helmet on a hot muggy day in heavy traffic. However, I have worn helmets in the past, on go-carts, off roading, etc. So I can imagine that in heavy traffic, sucking someone's too-rich exhaust, on a hot muggy day, those things have to be a royal pain in the butt. Especially if you commute on your motorcycle.
Now, I have been on scenes of motorcycle accidents. With and without helmets/other protective gear. Personally, I would never ride a motorcycle in traffic without at least a full face helmet and probably leathers and good stout boots.
However, seatbelt and helmet laws reek of nanny-stateism. Personally, I think that it's your choice whether you ride with or without either... BUT. You had better be sure that you can afford to pay for not only emergency care, but possibly long term care, as well as sufficient disability insurance to provide for your family if you turn into a vegetable after wiping out without a helmet. Because I've seen that one. Primary income earner gets seriously injured, ends up in a vegetative state. Insurance pays up to the max of their requirements for coverage, which doesn't even cover the ICU stay. Family is financially wiped out, and they end up turning to the state for help. Would a helmet have prevented it from happening? Impossible to know for sure, but it sure would have improved the odds.
Oh, and these?
There's a reason we call these "brain-buckets".