Lots of different possibilities. If there is regret afterwards, probably no cuddling. If the people don’t know each other well, another big possibilitiy no cuddling. If people don’t enjoy being hot, and they are already heated from the sexual act, they may want their breathing space and to cool down. If they had sex right before going to sleep, and they have a special sleeping position, they may want to get right to their sleeping position. All sorts of reasons for not cuddling.