That's a good question. As far as I know these losses are pretty epic, so it's somewhat uncharted territory. They're also not directly comparable to previous unicorns because of their cost structure. They also can't exactly amp up the website ads to cash in on advertising, like previous big losers who turned things around.
autonomous driving could potentially cut one of the main expenses (like the driver's fee), which could cut down prices even more, and probably get them enough of a margin to make them profitable.
that's probably why it makes sense to dominate the market while they still can.
Would it be fair to call it a Hail Mary if a technology that isn't ready for the mass market is a potential savior for a company losing $2 billion per year?
To be a Hail Mary it'd need to be a last minute risky play wouldn't it? I was under the impression that Uber has been playing the "lose money on human drivers until we have robot drivers and market share" game since, if not day one, a long time ago.