It may have been standard issue Imperfectionist but you're talking about a country that I suffering massively I terms of economy, plague, famine and civil unrest, how many of those suits do you think they can churn out in one year based on how badly the countries doing?
Also the vast majority of the T-51b suits will be on the west coast, and in Canada, what use are they on the east coast where there is no war?
That is the main theory on why the T-45d model is prominent in the east coast games, and the west coast games have all had the newer model.
So as Peligirno said the T-45d models will be used as a new form of riot gear and used to keep the peace. 
As you your self said, they're not worth their weight in scrap, meaning that they would be used for other purposes such as those outlined.

However you're are true In saying that there would be SOME of the T-51b models on the east coast but I still maintain the idea that there will not be many of them.