It’s very very useful when looking for bugs to at the very least have a central search, I’ve encountered issues before which are filed against a completely different app than the one I’m encountering it in (usually because the issue is actually in a library that both use), which I would have missed otherwise. Having a single database also allows then moving bugs between projects in cases such as that without having to recreate it and linking the old one to the new one.

Perhaps a middle ground would be to organize individual repositories under an organization, like on github, where the organization has a global bug tracker, as well as each project.