How does one get involved in technical committees in international conferences or commissions? How does one get involved in technical committees in international conferences or commissions? Does one need an invitation or does one volunteer him/herself? Also, why are many relatively more experienced or outstanding academics often not involved in these committees?

I think the first part of my question has been answered before in this site, but I would be interested to know the answer of the last part.
How does one get involved in technical committees in international conferences or commissions? Does one need an invitation or does one volunteer him/herself?


As you say yourself, this has been asked and answered. The executive summary is that as a first approximation, PCs are typically by-invitation and there is no "formal" way to apply or volunteer.


  Also, why are many relatively more experienced or outstanding academics often not involved in these committees?


Because time for "outstanding" academics is limited. You can only be in so many PCs before you do nothing but review papers, and for some very distinguished professors even one large PC may already be too many. Further, some conferences (e.g., ICSE) regularly rotate their PC).