In the earliest days of the new scooter sharing wave, when a new, Uber veteran-run company called Bird showed in southern California, working in the industry felt a bit like stumbling into the O.K. Corral. High school students scrapped for their chance to charge or fix scooters for between $10 and $20 a pop. “Mechanics” broke handlebars and wheels en masse, so they would be paid to patch them up.