Why were the disciples so concerned about their status within the group?

Why did the disciples, and the mother of James and John, seem so concerned about their status within the group of disciples? eg Mark 9 - but others too. I am wondering if there is more to this than pride - which is surely part of the answer. However, though as adults we are definitely concerned about our status, arguments between adults about 'I am greater than you' are far from common - in my experience. Is there some detail about the rabbi-disciple relationship here that is missed by a simple discussion of pride? Was there something at stake that is more significant than just 'I am better than you'?