Indeed, and there lies the problem. Additional staffing cost money.
Flamingo, Do you work on FGW HSTs? If you do, is it a challenge to check all tickets on an intercity run which turns into a 'commuter/short-distance' service at some point in the route? I would imagine this is an issue at First Great Western.
Yes, yes and yes!
The issue is partially the length of the train, and having to organise ticket checks around the requirement to be in certain places to avoid delaying dispatch, and partially down to numbers. There will never be 100% coverage, especially when the time involved in customer service issues are taken into account (answering queries, sorting out assistance requests), the delays caused by selling tickets to people who might not wish to purchase them, and any of the general buggerance issues (avantex playing up being the major one!).
I try to organise my ticket checks with a certain "random" pattern, not starting with the obvious carriage in some cases, or going straight to the carriage closest to the entrance at certain stations so as to get the most "bang per buck". I'll sometimes start in the middle of the train, or decide in a certain carriage I'll ask to check all ID cards from season tickets, or check the names against the ID cards. The randomness is useful, as it sometimes catches dodgers out. It's amazing the number of people who didn't have tiime to buy a ticket at London, but had time to walk the full length of the platform to coach A prior to departure
On the run into London, I'll always try to have a full check done before Didcot, so I can concentrate on the short-term passengers after Didcot. On the way out of London on a commuter train, if I can get 1st and 2 STD carriages done by Reading, I consider myself as having done well!
On a busy weekend train, it's harder. as there are a lot less season tickets, and a lot more people who require an interaction of some sort or another. On those trains, leaving London for Bristol Temple Meads or Swansea, if I get a full ticket check done by Bristol, I'll have worked my socks off!