My T told me it's because they want to separate the physical attraction from their emotions. My H agreed that, yes, that was what he was doing. But IMO, the physical attraction will eventually win out sometime, even if just for a little bit, which then reminds them of the physical connection.
It is tough. It sucks.
Me: 42/H: 37 T: 10 years/M: 8 D9, S8 Bomb: 7.23.07 Separated: 1.20.08 D Final 3.19.09 Affair started in '05, found out parts in 11/07. They married 11.26.09