I collect because I love history, and collecting coins is one way I can own a small piece of that history. I don't sell any coins, so profit means nothing to me, and neither does worrying about numeric grades. I don't collect graded coins so being competitive is also not a factor. You could also say that the love of beutiful coins (what I voted for), the pack rat at heart, and the escape from the stresses of everyday life combined is also a part. For me, I do keep everything in a particular order, and keep very detailed records, but I find that as a fun side effect, not the main objective.
If you have an additional reason please specify it in a response.