I used to get in trouble for missing calls and texts out of hours because they expected it. They expected it because I usually answered. I stopped and got in trouble a few times. Then they started calling someone else.

Likely you've suffered in less noticeable ways, like delays in promotion or pay increases

Is it really a widespread thing for people to get in trouble for not doing this

Yeah it is. Remember the whole "quiet quitting" bullshit panic? That was about people doing this and bosses (plus the pro-corporate billionaire-owned mainstream media) pretending that it was the death knell of businesses.

I've never answered an email or phone call while off work or on vacation and not once has anyone brought it up

Good. That's exactly how it should be. If they're not paying you for it, you're not on call. That should be a given.

The only people I see doing this are the people that do it of their own free will

Unfortunately, that's far from true. Lack of regulations. An obscene power imbalance stemming mainly from lack of unionization. A business culture that heavily encourages ruthless exploitation.

These conditions combine to make many if not most bosses abuse their workers in any and every way not specifically illegal and oftentimes even THAT doesn't stop them.

This law and effective enforcement of it is VITAL for labor rights and the mental health of workers