Varma boy and his ilk may give several reasons which mean nothing.
The real reason is — if one has to make a cost analysis of marriage over a reasonably long period of time, one needs to know how much a woman will cost, for one night; or day. For sex, that is. If you want love, the answer lies in sexuality — not necessarily sex.
The problem with it being illegal is, there is no set price and we can’t have healthy competition decide the rate. Prostitution being illegal, I am sure, is one of the reasons why Hedge Fund Managers make horrendous mistakes and why we have a credit crunch. Greed is, after all, a result of insecurity.