a) it is limited to make sure it is worth something, just like gold or other valuable materials
b) just because it is decentralized does not mean it will remain volatile. Sooner or later it will come to a stop
c) because you cannot spend it twice like you can with traditional emoney
d) It sounds like you do not. It is not some kind of religion, it is just a technology
e) Many do, many don't. You have to understand how investments and projected profits work, especially in something that so many are interested in