Producing a single car uses a huge amount of resources both in the production line it takes and the materials that go into making it. Especially plastics.
If Nora had a perfectly serviceable and safe car putting out below government guideline levels of CO2, which is then sat in a car park to be partially recycled (takes energy) and then crushed (a good proportion of the materials will simply be cubed) and left to rust in a pile somewhere, this is a heinous waste of a perfectly usable vehicle.
How do you momentarily fix a broken economy? You inject cash into it, if it never gets fixed and all you do is keep injecting you get hyper-inflation and we're all using wheel barrows to take our cash for our loaves of bread...
The scrappage scheme will, in one or two cases, remove genuine bangers from the road and in those cases, fine. However in most cases its being used by people as an easy alternative to a bit of haggling. The ONLY winners are the car manufacturers. Which on some levels is a good thing.
But to say "who cares, it's their life" is very short-sighted. We live on a very crowded island on a relatively crowded planet, what one person does invariably will have a small but tangible impact on your life as well. If many people do it, the small impact becomes larger and more evident.