Is Bitcoin primarily a medium of exchange or a store of value? No financial instrument can be both things equally well. Despite what some Bitcoin proponents believe, specialization in one direction is inevitable (many people who seem to think it can somehow be both are the same ones advocating 'buy and hold forever'...).
I disagree with your premise. Bitcoin makes a fantastic medium of exchange (best in human history), and due to the predictability and certainty of mining new Bitcoins (at predetermined rates), and the lack of monetary inflation, it will also make a great store of value.
Please explain why one cannot both save and spend in Bitcoin?