Originally Posted by D.wyatt1
I didn't know that. But I do now
I think of them as being embedded systems - Android specifically as that was the original design. ChromeOS is a bit different, but still has a much reduced runtime. In Android I believe (not absolutely certain) that the libc library is actually built into the interpreter (Dex/Art/whatever); in ChromeOS I think libc is much reduced in size - including only the functions needed by the OS, and leaves out all the other libraries.
This both explains the boot speed that they get, as well as the more limited need for updates. But it also makes the devices a bit less flexible. Nothing says the full libraries can't be added - the system calls are the same either way... The biggest issue is access to the display. Ubuntu has solved that, though I'm not certain how they did it.