Why are homemade guns illegal?

I'm curious to know, why are homemade guns considered illegal in many countries? Isn't the right to bear arms a fundamental freedom in some parts of the world? Are there specific safety concerns or risks associated with these firearms that make them different from commercially manufactured ones? Is it due to the lack of regulation and oversight in their production, or could it be related to the potential for misuse and illegal activities? It would be great to gain a deeper understanding of the reasons behind this legislation.