Friends with benefits beware.
Often enough one person wants a friendship with benefits as a means of safely, conveniently and comfortably having a sexual relationship. That individual is completely clear that he/she is not in love and will not be falling in love with the friend. But then the friend has other ideas.
The friend wants a romantic and passionate relationship and hopes to transition the friends with benefits arrangement into just that. However, this needs to be something of a secret, to avoid creating a potentially unworkable and hopeless situation.
The person who really wants the friends with benefits arrangement is probably actively seeking someone else who is relationship material. It should be fine to let the current friend know exactly that. But given what’s going on within him/her, it is devastating. It feels insulting, disappointing and hurtful. The message may very well come across as equivalent to saying the friend is simply not good enough and never will be.
It happens that the one who is not in love senses or knows the feelings of the friend and holds back from being completely clear about his/her lack of love. This is in the interests of maintaining the arrangement that works for him/her.
This is a really risky situation for the friend who is emotionally involved. Whereas the relationship could turn into what he/she wants it to be, the odds of that happening are low. Very often, people mean it when they say they’re not in love and there’s no potential for them to fall in love.