Numerous reasons:
- A protest against "too big to fail" banks and the current bailout culture
- Hedging against endless quantitative easing and money printing
- Privacy concerns over the increased surveillance of our spending habits
- Some have moved to Bitcoin out of necessity as their national currencies are collapsing
- Censorship resistance, so no one is able to block or reverse your payments
- Your personally identifiable information isn't required, so there's less risk of identify theft
- Freedom and independence, where you have full and total control over your money
All of these are things that should be plainly obvious by this point. After nine years, you'd think people would have got the message by now. Just because some short-sighted people are trying to use Bitcoin like a get-rich-quick scheme, doesn't mean it is one.