Just familiarity. Mostly I just can't recommend something I don't know much about. The SIMD variant of MT is architecture specific, I thought? Other newer variants of MT/WELL generators and PCG are probably all good options. Also xorshift*.

But I know that MT is a very good algorithm and using it has a certain pragmatic appeal - you make a lot of people's lives easier because when they Google to learn more about your generator they'll find good information quickly.