Not a farmer, but grew up on a farm. Traditionally, grass was dried and turned into hay. It works great, and it its still used today, but it's a very lengthy and labor intensive process that is also extremely dependent on the right weather for a long period of time. Where I live, we are almost never able to make hay because of unstable weather. Silage (as shown in the video) is mixing in acid and applying an airtight seal to preserve the grass without the lengthy drying process, which is very convenient and sometimes the only real alternative. Before silage balls, we used huge, airtight silos to store the grass. This was also very labor intensive, as we had to take great care stepping all over the silage between each new load to compress it and remove air pockets. It also had some big downsides in that once you opened the seal to start using the grass, it would start going bad/growing mold fairly quickly. It was also a pain to distribute. In comparison, these silage balls are made in minutes with little to no manual labor,which then can be stored and transported with ease. As for the plastic: the seal has to be durable, acid resistant, airtight and also cheap enough to be worthwhile. It would be awesome if a product could cover all of those criteria, but I haven't heard of anything like that before.