I do sometimes feel for the passengers who are getting on below the situation, as EMR passengers at Derby and Liecester are probably finding out today. They have booked an AP ticket and have a seat reservation. They go for thier seat to find someone who got on a Sheffield sitting in it. They ask them to move but they view they are entitled to it because thier train was cancelled.
I had it a lot when Hull Trains were operating the class 180s. The Hull Trains passenger thought they had more right to the seat on the LNER train then the LNER passenger. LNER then needed to pay compensation to thier own passenger for not honouring thier reserved seat, because they helped out HT. I think the LNER crew were getting pretty sick of it, as they were not only taking flak from HT passengers, but also there own.
I am sure EMR are feeling that pain today when a loyal customer wanting to do say Derby - London is seriously "turfed out" thier seat by an LNER passenger.
I am not sure if it is a combination of things that have changed that have made the MML worse at assisting. During a closure of the WCML one I did St Pancras - Manchester via Sheffield. The HST was full and standing but everyone got on. The 158 between Sheffield and Manchester was cosy but I am not aware of anyone left behind. However as you can tell by the train I mention, this was a while ago so there were probably less passengers. MML may not be suffering as badly now if Avanti (and TPE) were running a dependable service. I am sure if 3tph were running to Manchester some Leeds and York passengers may consider that way.