The barrier to entry is that they're building a marketplace. Building a marketplace from scratch is hard: no driver wants to drive for a network with no riders, and no riders want to ride a network with no drivers. To make it work you basically have to pay drivers to drive empty cars until your customer acquisition gets enough riders that the market is self-sustaining. That requires a lot of capital. If you follow that game plan in one market against a national monopolist, they'll cut their pricing in your market to drive you out of business. So really, you need enough capital to mount a credible attack in enough markets that the monopolist is better off accepting duopoly profits than burning what it would take to put you out of business. That's a lot of capital to raise and a lot of hassle, and you don't even get monopoly profits if you win. As a result, you'd probably have trouble raising the money. That's the theory anyway.