There's another step at the beginning: after you have a problem, you search for similar projects that might have already solved your problem.
And in fact this step seems to generate most of the bug reports - you get "please implement feature X" and "does this have feature Y?" and so on, from people who have used your software for all of 5 minutes (or not at all).
It's only after a lot of time is wasted that a new project is started. Alternatively, it could be that the people who try to use/reuse software and the people who write new software are completely separate, so that no amount of bug tracker work will lead to new source contributions.
And in fact this step seems to generate most of the bug reports - you get "please implement feature X" and "does this have feature Y?" and so on, from people who have used your software for all of 5 minutes (or not at all).
It's only after a lot of time is wasted that a new project is started. Alternatively, it could be that the people who try to use/reuse software and the people who write new software are completely separate, so that no amount of bug tracker work will lead to new source contributions.