How many of <T> ethnicity are in the community?

What is the average level of commitment and capability of <T> in the overall community?

If that is low relative to the community distribution members of <T> may not feel comfortable seeking speaker slots simply because they understand their relative ranking and do not want to potentially disrespect the group or humiliate themselves.

This is completely normal behavior for all <T>. Even in large subgroup most people do not consider themselves worthy of speaking at top conferences.