Prostitute use sex as a means to ask for favour or money and they get the favour or money after you are done having sex with them,,there is nothing bad in a wife asking favour from her husband,infact she has every right to ask for favour from her man same way he can
ask favour from her too,,but when you begin to use sex as a tool to ask for favour then all is not well in that marriage and asking for favour by using sex might sound like prostitution but i believe it is not because the
woman might find that action as the only way to get favour from her husband especially if the man is a type of man that do not care about her and would not want to do her favours if she does not have sex with him,but
whatever the reasons are i believe that such things should not be happening in a marriage if they both love each other and also respect each other and care for each other...