It is simply not sustainable to scrap stock that is not life expired. No industry can do that without costs having to rise significantly. I would maybe accept an argument for that if it were that the new trains being entered into service provided such an improvement in passenger service that passengers would pay these increased costs. But pay extra for an 802 over an HST? A 385 over a 365? I wouldn't pay extra for either
I don't think anyone is claiming that it
is sustainable to scrap stock that is not life expired
in the medium/long term.
But we have a situation where stock needs to be accessible from 1 January 2020 and a lot of trains don't currently meet those criteria. So a lot of "non-life-expired" trains (however you define that - it's not a black/white thing - some last longer than others) are going to have to be upgraded which costs a lot of money and means a TOC being without their trains for a while - witness the short-formations on EMT services recently.
We also have a situation where TOCs can order one large fleet at a cheaper rate than the motley crew of "heritage" trains that they inherited from their predecessor, so it becomes cheaper/ easier to order a big fleet of new trains.
Look at the GEML or Thameslink - lots of different types of EMU all doing the same kind of job (but with the complications of not working together/ needing separate maintenance/ needing separate training etc) - you could get a huge fleet of 700s or 720s to do that job - you could argue that the current problems are the inevitable hangover from the days of ordering lots of small fleets in piecemeal fashion and it's more sustainable to bite the bullet and order simpler/ bigger/ cheaper fleets of homogenous trains (though this will seem quite boring if you are a trainspotter who enjoys the variety of micro-fleets etc).
There's also the point to make that a number of lines have new trains planned whilst there's no guaranteed home for the older trains, but that's not the same as scrapping modern trains - stock like the 360s or 379s will find a home - there are going to be lines like Corby that require EMUs which haven't been announced yet - there are areas like South Eastern which have hundreds of ex-BR trains that will need replacement.
Plus, the actual cost of hiring the train is only a small part of the overall cost of the railway - compared to track access charges/ fuel/ drivers/ other staff - it's not like ticket prices will need to double any time soon.
The ROSCOs have known of these problems for many years - they have done very little to react to the necessary changes - I don't think that the rush of new trains will continue at such rates post-2020 but something needs to be done in the next couple of years, and if the ROSCOs aren't evolving then they will be left behind.