How does presenting and buying a ticket at a booking office make any difference?
Your aware those on priv ticket will be staff? If they're getting all irate at being checked then it's indicative off the culture on the railways.
In fairness it does make a massive difference.
Try telling a passenger the standard single they want to buy onboard is nearly triple figures and they can’t use their railcard compared to buying the single figure advance at the station or online.