Im an Asian American male, and a greeting is hit or miss for me, especially on boarding. But Im usually proactive and as soon as I step in the plane, I say Hello and its always returned. Similarly, I always say "Thank you" on my way out, whether or not they've initiated with a good bye.

I have never noticed that I got a hello/goodbye but a non-Asian who preceded me or followed me didn't, so Im not really buying OP's accusation of racism.