Last year Apple laid off most of the engineers it hired to design its own car. Google (now Waymo) stopped talking about making its own car. And Uber, despite its sky high market valuation, is still a long, long way from ever making any money, much less making its own autonomous cars.
To paraphrase Elon Musk, Silicon Valley is learning that "Making rockets is hard, but making cars is really hard." People outside of the auto industry tend to have a shallow understanding of how complex the business really is. They think all you have to do is design a car and start making it. But most startups never make it past the concept car stage because the move to mass production proves too daunting.