Why is piston knurling all the rage on YouTube?

It's click bait started by Uncle Tony...but seriously...a short answer and to stay on topic apparently it was once used as a cheap overhaul fix to get another year or so out of an engine. It cleaned up piston to bore clearance without an overbore but keep in mind this was prob back in the 30s and 40s when cars smoked and nobody cared etc. so Uncle Tony read it somewhere ran his mouth and his loyal followers lapped it up like dropped ice cream off a sidewalk.