Well, this question was asked. Here are my 5 points in answer:
1. It's fun! You can indulge your inner artist, child or just for the fun of making something.
2. It's a good diversion which can become a passion. When I was Ill last year, I needed something to take my mind off everything, and crafting fitted the bill!
3. It's productive. You have something to show for your time.
4. You can make new friends. I have found out that some of my friends make cards too. I didn't know before, but when I mentioned it.........!
5. It's calming and meditative. I can while away hours before I know it! :)