A good book on why those capitalist Platforms are hiring and investing a lot on becoming "the most perfect platform" is Nick Srnicek's Pltaform Capitalism ( https://www.wiley.com/en-us/Platform+Capitalism-p-9781509504... )
Most of their profitability comes from becoming a de facto monopoly / middle-man so they will attempt to gain as much market share as aggressively as possible. (Including sacrificing present profitability, giving away money for free rides/things, etc)
It is not a technical necessity but an economic venture capital necessity.