What can I do if my supervisor does not publish my research results?
This seems like a strange situation, since it is very counterproductive for both you and your supervisor. If this is indeed common in your group, I am sure several ideas have been scooped by the time they finally get submitted. Unfortunately, I really don't have any decent idea why your supervisor would act this way.

The most important thing to do is to talk to your supervisor and don't let him/her dismiss the issue. This may seem like an aggressive approach, but you can disguise it as a learning experience, e.g. "Please tell me what is wrong with the current manuscript because I believe it is ready for submission, oh wise one". Whatever you do, remain polite.

A few approaches you can try (all of which are reasonable, so don't be shy):


Send reminders and send them often. Ask what you can do to improve the manuscript. If your supervisor has no further suggestions to change the manuscript, ask where you can submit it to directly. Don't wait for him/her to wake up. This approach may lead to your supervisor turning it into a ping-pong match, asking you to make trivial but time-consuming extensions again and again. In this case, confront your supervisor and explain your perspective.
If you can find an appropriate call for papers, ask permission to send the manuscript there. Calls typically have deadlines and are not necessarily a downgrade in terms of venue quality. This includes conferences and journal special issues. Having a hard deadline might help.