I think this is part of the problem, numerous different TIS's to learn, a booking clerk at Avanti/Virgin over the years will have had to learn numerous different ways to issue tickets.There are multiple ticket issuing systems in place, all with different ways of bringing up those tickets.
From my recollection Tribute, Shere Smart, Avocet and now moving onto PICO imminently all with their own set of peculiarities for staff to learn and remember.