Patched streets, construction stone, and a lot of time sitting behind somebody's rear tires. We spray a clear protective film over your paint so all of that lands on the film instead of your finish.

Most paint does not get ruined in a moment. It gets sanded down over a few hundred small ones, and by the time you notice, the fix is a respray rather than a polish.
Allentown streets get cut open and patched year after year. Loose stone sits at every seam, and the car in front of you flicks it straight at your bumper.
Crawling traffic puts your nose a few feet behind someone's rear tires for miles. That is the position that throws grit at your paint, and rush hour holds you there.
Downtown decks and street parking mean door edges and bumper corners take hits that have nothing to do with driving. A coating will not stop a careless door, but it takes the light stuff.

What goes on is a clear film, 8 to 12 mil thick, sprayed in a downdraft paint booth rather than cut from a roll. It cures into one continuous layer across the panel.
Because nothing was cut, there is no edge at the panel gaps to collect grime and start lifting. Because it bonds mechanically instead of with adhesive, nothing is glued to your clearcoat.
Light marring sands and buffs back the way paint does, and years later the whole thing peels off in sheets with your factory paint untouched underneath.