I would say prostitutes are useful because men need sex. they need sex for many reasons, some are because they are bastards and hate women, but I believe that is the minority. Alot of men want an escape from stressful lives, you wife may not be interested in taking care of your sexual needs, cos she is selfish, or feels like she can use sex to ransom you. therefore you can just pay for this service.... its like a good foot massage!
If wives take care of men like prostitutes take care of men, listen to their needs sexually and fuck them properly, no man will ever go to a prostitute
thankfully for the industry, women are not so perfect.....