There is a lot of science behind it actually. There is a post-coital crash for even healthy people. And over time, due to the Coolidge Effect, cllmax actually pushes people apart.
I'll bet when you had sex without cllmax, you felt more snuggly aftterwards. It keeps oxytocin higher.
Whereas after cllmax, you don't really feel like being with the other person as much.