Why does he like this?

When I put my baby down for a nap in his baby swing the only way he’ll go to sleep is if I sit there and swing it hard until he falls a sleep. Why does he like this? And also could it be bad for him to be swung hard in the swing? It’s not too hard but definitely a lot my force then it just swinging by itself. He’s the same way in his car seat. He’ll cry until I pick him up in it and swing that too.