The vast majority are NOT making six figures. The work is hard, has long hours, and is physically exhausting. My grandpa was a welder/machine shop owner my uncle is a electrician. They would trade anything for a cushy desk job with great pay, great benefits and easy workload. I've never worked past 4pm and have ample paid vacation time. They will never be able to say that. Google says that here in Austin TX, the average master plumber makes $25 an hr. HVAC is the highest at $44 an hour on average. And we are going through a construction boom, also don't forget that you have to factor working in 100 degree heat and 50% humidity 5 months out of the year.
Sure you can start a business and eventually have 5 workers and 3 trucks like my grandpa but then you become a entrepreneur and have to deal with the whole billing, scheduling, selling, headaches of running a small business.
I find a lot of tech people idolize the blue collar fields. It's damn hard work.