Before I was a mum I used to think it was a bit mean but when I was shown how to swaddle my DS I saw how relaxing and calming it was.
If you think about it, because babies haven't even begun to master control of their arms and legs, when they get upset they kick and thrash and it must be a stressful sensation. It must feel good for something to hold them tight and stop that feeling of being out of control.