Do you need to know Joe bought a coffee for 3 btc in September 2009 ? I dont think so, thats why deletable blockchain (as a feature, not an obligation) is useful. Nobody needs the whole chain to use PascalCoin, but you can keep it if you want, if you are a merchant or just want to verify all, but thats not an obligation and it allows low end computers to download less blocks, sync faster and be light peace