Maybe it's just that you don't have much control over the dream, or it could possibly be stray thoughts manifesting your dreams. It's hard to tell why some people dream of what they do, I know myself I've had a lot of dreams about things I would never do in real life, though not in a lucid, not that I've had one long enough to find out, anyway. I'm sure with a bit more practise, you will be able to find out what is causing it, and fix the problem.

Good luck, and happy dreaming