There's a hell of a lot of inefficiency with men being taxied everywhere, but in part this is due to privatisation, as staff from different companies can't generally work each others trains unless an agreement has been made, so it means men being taxied to one location, even though it may have a depot for another company and spare staff.
Besides inefficient as it is, it's the train operators money, and it's better than cancelling services from the point of view of the punters.
It doesn't cost anything in the long run though as they just put it against tax! As for drivers driving on unsigned routes, isn't that why the Sutton Coldfield crash back in steam days? driver didn't know the route so was doing 70mph on a 20mph curve through the tunnel?