Maybe because they are fun and relaxing? Not everything has to be some intense FPS...
I've been playing games for decades. I like casual games, hardcore games, PC games, console games...you name it. I don't know why so many "gamers" diss casual games. Casual games are just like hardcore games. Some are great and worth playing. Some suck. Find the good ones, no matter what genre, and play them. And skip the crap.