Anyone use an airbag vest?

I never seem to see these mentioned amongst casual riders, and always assumed they’d be stupidly expensive or only used on track.

Some basic research today taught me that high spec ones are barely more than a lightly padded vest needing only 4cm room under your jacket, and even these are sub $1k.

What’s the consensus? Are they a gimmick, or overrated? Do they offer anything that a normal reinforced jacket doesn’t?