Original: Another, however, believes that legalizing and regulating prostitution does not improve the situation, but instead makes it worse, creating a parallel illegal prostitution industry, and failing to dissociate the legal part of the sex trade from crime.
Simplified: Other people see a different problem: Legalizing prostitution would lead to some legal prostitution, that would well-regulated, and probably worked well. On the other hand, there would also be the illegal prostitution, which would not change much.