The same reason why people still run Apple ][s and Commodore 64s and old DOS machines: nostalgia.
I mean, if I were to try and build myself a real Jurassic Park workstation, it would be a disservice for it to be running Linux on an x86. No, I want the real deal: IRIX on MIPS, complete with an animated Nedry confronting unauthorized users with "Ah ah ah! You didn't say the magic word! Ah ah ah!".
And yes, I'm aware of jurassicsystems.com, but it just doesn't feel the same. It also doesn't have `fsn`, so I can't zoom around my filesystem in 3-D while muttering that "it's a UNIX system; I know this!".
For driving demand, they could always have tariffs, etc. If they applied to companies manufacturing computers in China, that'd have a massive impact globally.
That said, the smartphone market in China has been dominated by ARM chips. The real question is whether there's enough market demand for a MIPS-based architecture right now, or if the Chinese government can drive demand away from ARM and towards MIPS.