TBH, OP, It most likely is not you, your skin colour or how sweaty you are because I have sat next to a lot of sweaty people of all different racial identities and plenty of them Asian/ local.I feel that it has a lot to do with personal space. Younger people prefer their own space than being crammed up next to someone they do not know.
I'm white and yes, I like a seat to myself also, namely as I don't like people standing or sitting too close to me regardless of skin colour or race. I've had young city boys fall asleep early mornings and late evenings on my shoulder while on the MTR, add to that the snoring...But having lived and travelled in other countries, Asian and not, the personal space thing and age does ring true. Older people are not so concerned but younger people are, for some reason. I am just speaking on my own experience - even here in Sweden, people will go out of their way to avoid other people, even those they know if they can. So OP, don't take it personally. It is not you, it is them.