In the recent fare rises, some child fares went up from 50p to 55p. And as if a 10% rise were not bad enough, there is an additional problem: most POMs don't take 5p pieces, nor do they give 5p pieces in change. So if the ticket office window is closed, then youngsters can't buy a ticket.
When ticket office staffed enquired about this illogical decision, the reply was "we never thought of that". Which strongly suggests that if workers made the decisions, we would make smarter ones.