Plumbers, electricians, lots of other sole proprietor workforces in the trades have unions that institute strong training and protection for their union work. Is it perfect, nope. I can't stand police unions in my state because they prevent perfectly reasonable road crews from functioning with only flag crews instead of with flag crews and a usually sleeping officer just to pad their wages. There's some crappy things about unions but it's the only effective way to protect individuals from companies. They don't however protect companies from outsourcing, usually to lower paid non union workers of lower quality.