coffee is not a legume. It's just called a bean because of it's resemblance to true beans
Coffee bean - Wikipedia, the free encyclopedia
I drink coffee because I like the taste. The caffeine probably does have something to do with it, but I recently missed having my morning coffee and didn't go into withdrawal. I also like tea, but can't drink it on an empty stomach. It makes me nauseous. I drink 2 to 3 cups a day.