Linux literally ate the world with its POSIX-compatible open-source proposition. I don't have a single device without Linux at home, and this includes a NAS, 5 notebooks, 1 PC, a handheld gaming console, my TV, a bunch of mobile phones, a washing machine.
The world just couldn't care less if it is a microkernel, a hybrid or a monolithic kernel. Like you said, it's not about some boring technical advantages, and it never was.