Seriously, usually even when two people sleep together outside of a relationship, only one person is completely indifferent to the possibility of a relationship (probably the guy).
for me, the bonds i feel in platonic relationships are actually noticeably stronger than those i feel in sexual relationships
when the person i'm having sex with decides to stop having sex with me, i feel sexually frustrated untill i'm able to have sex with someone else
but when the person i'm talking to everyday (the person that refuses to have sex with me) decides to stop talking to me, it hurts a lot more, there seems to be a much stronger bond there
yes, i actually care about the person i'm having sex with, making them orgasm, selflessly making them happy in non-sexual ways, giving them thoughtfull gifts etc etc etc, but for me there's just a stronger bond with my platonic buddy