Why PPCoin is using the coin age for proof of stake instead the coins itself?

Hi all,
I have some questions about the Proof of Stake concept of PPCoin.
As far as I understood, you use the Coin age for proof of Stake.
But isn’t using the coins itself much safer than the coin age?

Best regards,

P.s.: Don’t understand me wrong, I like the idea, that you get new coins according to the coin age if you take part in securing the network :wink:

Interest is based on time, so just because you have some coins it does not mean that they would be eligible for interest payment. You get paid for the time that you kept the coins thus it is based on the coins’ age not the coins themselves.