Even legalising prostitiution does not cut out the pimps.
In Holland, for example, there is an horrendous underworld of illegal prostitution - sex that is not allowed to be provided legally.
Without condoms, underage sex are examples. There is also a large number of 'sex slaves' in Amsterdam, women who have been trafficked from other countries and are forced to work as prostitutes:
http://news.bbc.co.uk/1/hi/world/europe/461626 4.stm
I will never understand why men pay for sex, especially in the UK where girls give it away freely, but it really doesn't bother me so long as both parties are truly consenting.