Why do we write?

Anyone else ever feel like this? I have wanted to be a novelist ever since I was little, but that hasn’t really worked out and I now have a really demanding day job. Every so often I’ll see a call for submissions or a competition and think ‘maybe this time’ - but they always end in total failure and it makes me really sad. Even so I can’t seem to stop writing! When I’m in the flow, just creating, it feels great. I just can’t really escape the feeling that it’s a bit pointless.

EDIT: Wow! Thank you for all your responses. It's so inspiring to hear your genuine passion shining through. For those who are striving towards publication I wish you the best of luck - for those who are just writing for yourselves, I'm not sure you need it!