Why isn't dating criminalised under Sexköpslagen?

When men take women on a date they pay for drinks, food etc. with the expectation that the woman will have sex with them later (or after a few dates). How is this different from prostitution? If it's illegal for men to pay for sex in Sweden how can they legally date?

Alternatively, if treating a woman to a meal in exchange for sex is legal would it be legal for a man to pay a prostitute with food or gifts?