THE CLASH OVER classifying Uber drivers as independent contractors versus bona fide employees is the signature controversy of the on-demand economy. According to Uber, Lyft, and other on-demand driver companies, the independent contractor model offers the promise of a bright and flexible future in which each worker is a micro-entrepreneur—choosing her own hours and acting as her own boss. The problem, according to Uber detractors: these workers don’t receive benefits. And they can’t unionize.