I don't know any tech execs and I am only remotely familiar with the military, but I am hazarding a guess that the cultures in tech and the military are not at all similar. I'm also guessing that there is a massive difference between fighting for Ukraine by using your tech skills and participating in a time-limited, no-real-skin-in-the-game learning exercise.

Not to mention that at the same time this is happening, SecDef fired a number of generals, and the military is being used for political purposes, at least according to some.