At Ledbury the guy running the ticket office, up to a few years ago was is a one man band,
so no issue, in my opinion, with him selling tickets.
There are / have been a number of agencies - Chester-le-track, Llandrindod, Looe. Business tickets sales at the Trowbridge
TIC▸ . Something I have had an eye on over the years / when buying your ticket before boarding the train, and getting the right fare from the baffling array of options, has been sufficient of a hurdle to put a number of passengers off. There is or have been significant overheads involved - it's not as easy as just putting someone behind the counter as a shop assistant.