The trouble with governments is that they are always telling us what and what not to do for our own good.
A few years ago, it was: drive diesel because that will save the planet. If they had paused a moment and possibly asked Autocar, we could have told them that never mind about a naturally occurring gas coming from petrol cars, diesels are rather more evil.
Well, for the short-termist, quick-fix politician, it is now time to think of another clever wheeze to get people out of their rotten old diesels and into something much newer. Hence the proposed schemes.
Scrappage ones are meant to be stick with a side order of carrot. You give up a perfectly serviceable vehicle for a discount on something much newer. It sounds like a good deal.