I have never run a brothel but I have managed escort agencies for years. Brothels are very useful to people who own escort agencies because of supply and demand. If your escort agency is successful you will have times when there are more clients than escorts. Which is a problem because that means that you lose the money from those clients. Even worse, those clients might go to a competitor and you might lose them forever. So clever escort agency managers make sure that they have an agreement with a brothel. That means that they can get more prostitutes for when their own escorts are busy or not available.
Prostitutes are reputed to be stupid and forced into the sex industry. My experience is very different. Most of the prostitutes that I work with are clever and good at their jobs. Not all of them obviously. Some high class London escorts are stupid and lazy but not many. There are some prostitutes who have been tricked into the sex industry or have been smuggled. But I have been in the sex industry for many years and there are very few slaves in the sex industry other than on the streets. Girls who offer cheap sex might be tricked or forced into working as prostitutes. But women who work as high class prostitutes are in the industry because they choose to work as prostitutes.
Lust has been the greatest force in human history. Society has mainly been built by men with power. Many of those men have become successful and gained power so that they can get more sex with women who are more beautiful. Lust for sex motivates men to become rich and get power. Women have been attracted to men with power since the first days of human society. So men are attracted to winning power because they want to have sex with the most attractive women. Men want sex and power. Women want security and sex. Sex and lust are what make people the way that they are and people have made society.