People who have sex with people just because they enjoy it already exist. It's not new and it won't meaningfully increase just because a society becomes currencyless.
Without an economic incentive, sex workers will stop existing entirely. It won't be work, and they won't have any need to do it. They won't be compelled to have sex with you just because you have money now. There will still be people at a bar, club, or whatever who will have sex with someone they like for little or no reason, but again, that's not new.