I imagine MIPS (via Atheros, Broadcom, etc) was broadly deployed in things like home routers because it was royalty free, power efficient, and already had Linux kernel mainline support. Though probably losing share to ARM now.
Indeed, Asus moved from MIPS to ARM between the RT-AC66U and RT-AC68U, and the various *pkg repos have since dropped support. MIPS may as well be dead.
