I can only say that, in my experience, the answer to the thread title is (or rather was) , yes .
   Certainly,those members of "The Oldest Profession" with whom I had any dealings in Hong Kong, Singapore,Edinburgh and Plymouth, all appeared to be quite happy with their chosen life-style, were not,as far as I was aware ,drug-addled single mothers,and showed no signs of having been coerced,threatened,or mis-treated in any way. Indeed,they were pleasantly "normal" in many ways ; the "proprietress" at the establishment in Danube Street, Edinburgh, was charming,polite,and courteous, as were her "staff",who were,frankly,delightful,and the ladies in Hong Kong were utterly charming too (and beautiful !).
             Why did I do it ?? Well,in each case I had been at sea for some time,and was a fit,lusty ,20-year-old .So what's your problem, you who referred to "poor sad bastards" ?? Get a life, man !! Mind you,that WAS 1967 ; I think that things were much more laid back (no pun intended) in those days.