Russians never throw away any weapon. However, as these 50s design anti tank guns were supposed to be obsolete by 90s and already in museums, it is surprising to see these in such vast numbers. Noteworthy is the very shiny example at 34sec mark, it has white wheels marking a parade version.
I have no clue if those are really on their way to the front, but as none of the others are white wheeled those aren't going to the may day parade. Talking about scraping the barrel. It just happens there are loads of barrels to scrape.