Might be because Men are waking up to the reality that they can make more money going to a trade school.
In the trades, after the job was over or I had turned over to the oncoming shift operator, I didn't think about work at all until my next shift, it was great, my off-time was mine. It was much better mentally compared to now where I have to have my phone on me at all times and respond to emails from our customers (granted, my customers or Transmission System and Distribution System operators controlling the electrical grid, so it is pretty critical when the applications experience issues). There are pros and cons of each, with pay being roughly equal (outside of the major tech hubs). Am I glad I switched? Sometimes, but the skilled trades (electrician, pipe-fitter, plumber, HVAC tech, welder, etc.) are definitely a good way to go if you want to learn a useful skill and have a relatively stable middle class life.
For example how many Floridian contractors know about Bora Care? From my interactions, few. It poisons wood. Termites can’t eat it. In Florida you can charge an extra 1k for a house and permanently protect the home from termites. Few even know to offer as a perk on restoration. Think about it, for $75 plus labor a reno contractor could termite proof your kitchen studs while they redo the walls. Poor training.
Home renovation is also where a lot of bottom-feeders end up. It's very easy to do and doesn't require much skill to get into.
When I was talking about skilled trades I was mainly referring to your union/licensed/Journeyman types. We had continued training programs to keep up with latest NEC/NFPA/ASHRAE/ASME changes. We also had the option of teaching at the union hall (all apprentices work normal days and go to training at the hall on Tues/Thurs) to earn a little bit extra money.
I've met good craftsman as well as lazy ones, but like you said, now that I'm a full-time developer, the same still holds in our industry as I'm sure it does in most industries.