I honestly cannot remember the last time i actually used a ticket office. Actually I can, it was activating my Japan Rail Pass and booking Shinkansen tickets in Tokyo.
In the UK, it must have been around 2009 to get an excess added to a single i had bought on a train as i had forgotten my railcard at home and bought a single on the train.
Even at Leeds which is a major station, i very rarely see more than 5 people queuing for the ticket office there. I suspect at many smaller stations if there are offices, they are mostly only open in the morning peak.
I struggle to believe that many people are coming to the UK and struggling to know how to travel on the underground. Going to Milan, Lisbon, Tokyo, Kyoto, Singapore etc... i looked up in advance what i needed and how to get do it. Very few ticket offices there.
In fact, the only place where there was a significant number of booking offices and staff was Japan, but the sheer numbers of people involved there i suppose makes it worthwhile. Rurally there were very few ticket offices again.