So why is illegal to give a gift to someone who gave me an mage?

I know that PAYING for an mage is illegal, but why is it illegal to give a gift for someone that wants to do me a nice favor of giving me a sensual/ mage with NO involved? I mean, anyone can give a gift no matter what kind of gift (cash, jewelry, etc) and if the person who is willing to give the mage (no involved) is not setting any rate or fee for this gesture, then why that is illegal? because in that case, many women can be arrested for being with men just because they pay for their expenses and spoiled them! so this "illegal" thing for a sensual/ mage really doesn't make sense! can a lawyer or someone in the law enforcement explain me this in details? when is legal this kind of act?