http://www.keil.com/support/man/docs/c51/c51_le_ptrs.htm
http://www.keil.com/support/man/docs/c51/c51_le_ptrconversio...
Just like x86, it's likely that everyone interacts daily with a system containing at least 1 8051 core.
The biggest problem with those is, that modern compilers don't support it. Well, that is open-source compilers. IAR will happily sell you a license of their IDE for 2.4k$/seat. There is sdcc, but it's no comparison to a modern gcc or the commercial offerings.
Unfortunately you're right though, 8051 processors are cheap and abundant. Chip makers use it as the go to architecture for any simple embedded processing requirements. It's slowly changing though, but ARM licensing costs are still much higher. Let's hope that in a decade or so they'll use RISC-V instead.
Edit: I am mistaken, it seems that though MIPS is used in all sorts of things that I'd expect wanted the cheapest possible CPU core it has only become free for academic use. I wonder how common that mis-conception is for those not active in the space?
Home routers usually have MIPS CPUs and run Linux on top of it. This wouldn't be possible with the 8051.