Just start using one

If you just start using one you will begin to realize their convenience on practice, much like version control software, or for that matter, distributed version control.

Development maturity

It doesn't matter if you have a team of 100 or 1, I started using bug tracking and distributed version control (makes a lot of sense because of local commits) for myself and myself only and I already felt at another level, but not only that, I could manage my work at another level... to a level it could scale without me investing more effort.

By using a tracker you can anticipate problems and prioritize work, bug/issue trackers are not only for bugs/issues, they are more for project administration, and each and every project should have that.