Prostitutes solicit at dockside nightclubs in Cape Town and Durban to make money for themselves. They care very little about the financial health of the club owners. The see the clubs as a business pick-up joint. And if they had it their way, they'd whisk away the guys as soon as possible and take them out for business.
The owners need women at their clubs, otherwise the sailors won't come. But they also need them to inspire the seamen to spend money on alcohol before going off for sex. Otherwise the club won't survive.
So there is a delicate balance of interests between the club owners & prostitutes. The owners put up the money for the joint, pay the levies, employ the staff, and so on. And their outlay provides a space for the women to solicit in relative safety and comfort. To cover these expenses and make a profit, they need the sailors to buy lots of alcohol. That's how they make their money. (The women pay very little money themselves, letting the seamen buy them drinks, cigarettes and food.)
The sugar girls know that their presence is all-important to the profitability of the club. Without them, sailors wouldn't bother to come. And the club owner wouldn't have a business. Thus they feel entitled to the bulk of the seamen's cash. While they like drinking and dancing with the guys at the clubs, they don't want them to blow all of their money there. They want them to save it for sex afterwards. So they try to leave with the guys as soon as possible, depriving the club of alcohol sales, but protecting their own earnings.
To arbitrate these competing needs and desires, the club owners have instituted a simple rule: if a prostitute leaves the club before 2 A.M., she must pay a fine of 100 rands ($14). This is called a "bar fee." It ensures 2 things. That bored women remain at the club (even if it is dead) so that the club retains a vibey atmosphere if any sailors might pop in. And—for women who leave with clients before 2 A.M.—the fee represents the money that the sailor would have spent on alcohol had the prostitute not taken him early for sex.
In this way, the owner doesn't allow the women to abuse his hospitality by coming and going as they please. For the privilege of soliciting at the club, the ladies must hang around even if there is no action and they must pay a fee if they take a sailor too early. After 2 A.M. though, they're free.
The women grumble about the rule, but they understand it. Heck, they even enforce it: if a woman sneaks off before 2 A.M. without paying the fee, her rivals at the club will make sure the owner finds out and fines her!