My cat loves to "help" when I sew too. I had just completed a top for my nephew, and it sat spread out on the spare lounge suite for a week, as the cat decided that she LOVED it. Try to get her off, and you would cop a swipe and a growl lol.
Another cat I had insisted on sleeping on my ironing board, same thing, try to get him off when I wanted to iron was like showing a red rag to a bull. I ended up getting a little iron board to use when he wouldnt let me use the big one.
Any yes, my cat does rule the house, she is my baby and I love her to bits.
Perhaps its the "Happy and relaxed atmosphere that is created when we do sew....hence the cats like to be around you to get the good vibes...maybe?? IT seems all of our kittys are the same lol