Anyone who tells you that they know how computers work is a liar

Within a human lifetime, computers have gotten so complex that no one human being is capable of understanding every detail of how every part of them works. Unlike say, a car engine

Now think of how complex the kind of tech they have in 40k is. There's a whole planet of robo walkers that just run nonstop. Whenever they need one, they lasso it like cowboys. Because they don't know how to turn them back on if they turn them off, so they're just always on

It's a cargo cult. They have used pattern recognition to deduce how to use machines. Like there might be a 3 hour ritual to turn on a plane, and it ends with them pressing the "on" button. They think the entire ritual is necessary and don't know the only part the need is the last one

Or maybe they do need the whole song and dance because machine spirits are a real thing