The Anonymous answer below is stupid. We go to strip clubs because men are visual creatures, and we're also lazy. We can give a stripper $5, and she'll shove her boobs in our face. Maybe a guy has a brunette girlfriend, but he gets really turned on my blondes, so he can go to a strip club, spend some money, and see some hot blondes naked. It's better than dumping his girl and going looking for a blonde.
Well it's easy. Just look at it like a space alien watching humans interactions. Men like to have sex all the time. It's really really hard to get their brain to not think about wanting to have sex. However, to have sex, a man would need to meet a woman (at least pretty in their book) and do the whole "mating dance" rituals. A lot of them failed at it, think that they will fail at it or just don't really like spending time on it. Some men will pay to skip the whole 'rituals' part for a one-night-stand.
Thus, this is why prostitution is the oldest profession. It's the one profession that will hang around as long as men still have money.
A lap dance in a strip club is closest a man can get to have sex with a pretty woman without actually having sex with her. Men will pay extra if they can have the wild fantasy sex they dreamed about after/during the dance.
The girls will rub their tight asses in the guys face for a little extra. And in some places will even give some oral stimulation. Plus it's much like any relationship, the guy wants the booty and shells out all his money for or to the girl. This just speeds up the process and can be casual.
Because their dumb asses. They hold onto to the hope that one day,that one stripper that they have given their hard earned money to will want them not just their money.Yeah right . Like I said their dumb asses.