That doesn't answer the question. What is the guard going to do? Say "naughty naughty, should have bought one before boarding"?
It's an icebreaker for any customer service interactions and gives the crew an excuse to engage with the passengers. I've posted on here plenty of times before that if you take the 'customer service professional' position that the TOCs now espouse for their train crew then revenue protection becomes far from the only reason to carry out a ticket check.
I'm protecting revenue on a pay train if I go up to someone I've seen board. Same on a regional service if I do a full check from the origin or en route.
If I say tickets please in a general manner I'm more interested, believe it or not, in getting amongst the passengers and having a chat, offering advice and having a general awareness of what is going on in the train. Revenue protection isn't particularly high on the list.
Much better than someone having to stop me when I am hurrying through the train.
It might cause me to spot the group who've had a few too many beers, or give an old dear who is a bit worried about something later in the journey a window to ask me about it without feeling like they're interrupting me or being a pain.
Ticket checks are a very useful tool for a proactive guard.
