Any individual endeavor
could lose money forever. They could be scooped by Waymo. Their super-popular RSS software could be cancelled. The future of communication could be WhatsApp, not Wave.
But they're able to invest in the future because they have the spare resources. Maybe one of these random side projects will become immensely popular. Maybe one of these crazy side projects will become the most popular email interface ever. And even if they don't, the people are still valuable.
I'm not saying that some people won't just coast, but the potential for innovation shouldn't be locked away because "we can't afford it" - we obviously can.