I see a lot of alt-coins use what is called "Proof of Stake"... That gives them an incentive to be full nodes, at least some of the time. Maybe not all the time.
Well then it's not impossible to implement. And yes this is just a debate for a request I made. See thread Subject.
One of
BTC strongest claim, is it's decentralized nature. {This is being threatened, by less people, running full nodes} Exaggerated but still true.
Why not implement something that is a incentive to keep it that way. {decentralized}
I suggest you read up on proof of stake. Bitcoin secures the network by proving that enough work (in the form of computing really low hash values) was put into generating a block that it would be (almost) impossible to have forged it. The proof-of-stake altcoins secure the network by proving that enough coin days were destroyed (I suggest you read up on what that means) in the process of generating a block that it would be (almost) impossible to have forged it. I have a much better understanding of how proof-of-work actually works than proof-of-stake, so I'm not really in a position to explain it better. But what I can tell you is that changing bitcoin over to proof-of-stake would be a huge change in the security model of the network. It would destroy some trust, and there's almost no chance it will happen without an extremely strong reason (stronger even than loss of some decentralization). The only way that could happen is if the current security model breaks somehow (51% attack, SHA-256 broken, etc), and even then other solutions would be considered first.
The reason not to implement something that is an incentive to keep bitcoin decentralized is that we don't know how to without either breaking trust in the network or adding an element of trust in a third party.