Under generally accepted accounting principles (GAAP), and their European equivalent, IFRS, a company generally cannot include in income payments it receives on behalf of others.
Lyft, and Uber, rely on the fiction that they are merely booking apps for drivers, so the fares belong to the driver, and Lyft and Uber are merely entitled to a portion of the fare for providing the booking service. At no time are they/were they entitled to the entire fare, so booking the entire fare as income flies in the face of good accounting--and, for publicly traded companies, the law.
The only reason startups do this is to artificially inflate their valuations. It's really not much different from cooking the books.