This has come up so many times. It has far too little memory for Linux, but ignoring that, the MMU is broken and can't support virtual memory (not that they claim to support supervisor mode anywhere).
Complaining that it doesn't support Linux is like complaining that a Honda Civic can't compete in Formula One.
It's the lack of full MMU that's the actual reason, it keeps the chip firmly in the microcontroller domain.
Memory is expansive, because Si chip area is expansive. The chip is designed for cheap special purpose applications. For that it fulfills the function.
Btw. you can run Linux on it, you just need to do something and can't simply put the latest and greatest Ubuntu distribution on it.