The sad part is that I only have one point of view, I wasn't able to talk to the man about theirs. But I find that once she indulged too much in it, she finds that sex means nothing anymore. She used to think that now they had sex, their relationship will be better. But now, I don't know what's her definition of love, but escalating to sex is quite serious.

Sadly, not a lot of people understand that love is more than just sex and associates that making love is love already.

Either way, sex is a serious stuff and shouldn't be done unless they are serious enough. It's my POV anyway.