That is probably part of it, but the work they'll be doing is more labor intensive. I was a union electrician/power plant operator for nearly a decade before I finished my degree in CS and took a job as a software developer. I'm not in SV/NY/Seattle so my pay is roughly equal to what I was making as a topped-out Journeyman, but the work is less stressful on the body.

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.