"We're just friends
" she says.
"Isn't it great we can sit and talk
all night long without making a move on each other?" he asks.
These are the ways we justify the fact that, while we enjoy the company of the other in question, we don't feel the need to "make it official" or to take the next step.
This situation seems to arise two ways: one is that a friendship develops into something more, two that a relationships divides so that the two parties can "see other people". Whether or not the relationship changes at this point is unknown, but I'm sure that it's about even for either way.