It all boils down to this: Either you wear the tools , or you take the courses , learn the lingo, hopefully learn the gannt math behind it (few actually do and still call themselves "project managers" while totally clueless as to what it really means to manage a project.) and mix in to the corporate crowd where it is easy to be a numbnuts ahd get away with it.
So choose- Electrician or Numbnuts.
If you are willing to stay a small shop doing residential or small tenant improvements, or even just a few projects at the same time, than PM isn't worth the effort.
But, if you are doing commercial of medium and up size, PM is an excellent tool.
Gannt charts are just one of the tools that are useful. And that's all PM is, a tool. It's not a magic solution.
When you have multiple projects on the go at the same time, the charts are very useful to allocate your resources.
You don't need to take a PM course to learn how to make/read scheduling charts because Microsoft Project will do the same thing. But understanding the premise behind Project Management will help you on larger projects.
Project Management isn't just Gannt charts. It's communication, QA/QC, risk analysis/management, procurement.