The thing is, if the RMT do campaign on this, it's only delaying the inveitable. Fewer and fewer tickets are going to be sold physically in years to come and whilst I appreciate the guidance that a ticket office can give you, some have done no favours to their grade. The cost of running them and the staff on a ticket/day basis puts them in the firing line. The vast majority of the population will happily use their phone / tablet / laptop / deskop / TVM to buy their more complex ticket, a percentage that will only increase. Have a look at
how few tickets are being told in some places on the Overground - yes its London and contactless and Oyster is prevalent, but it's a starting point on data.
What should happen is a multi-skilled station role with someone able to sell the core tickets on a machine like a guard and major hubs to still keep their ticket offices. That being said with the latter, having used Waterloo, Paddington, Reading and Liverpool Street all recently, they already only seem to have half the windows open and even then there's hardly a queue, even at peak leisure times. As for the land "theft" sounds a bit excessive and rather conspiratorial - many of these places might earn more money in retail rent that they do currently based on ticket sales, or they would remain as staff space or storage.
The direction of travel is only one way, although I do feel for the staff affected.