Because you become one who understands that the entire core of the power structure of our society today is rotten through and through. You understand this corruption stems from the fact that since the 70s it's been based on a debt based fiat currency which gives the hands of a few absolute power to create infinite supply of this currency that we sell our time, labor and goods for every second of every day. You also realize that if we can change that core to one where it's based on a non governmental /non corporate controlled hard asset that is the world's first truly finite asset that the people of the world get to decide on the value (supply) that we can take the next step in human evolution and create a world that rather than the current fiat masters, that we all collectively decide what our time is worth and not the other way around.
You realize that it is truly possible to achieve this but that the only way to do so is to take physical possession of your private keys away from any custodial solution as you understand that possession is 10/ 10ths of the law with bitcoin and every Satoshi counts. You then become one of us. One who regardless of what the current fiat currency value stamped on these banker backed exchanges is that you dollar cost average every time you get any extra money. You do it because you want a better future not only for yourself, but also your family and friends. You see it can happen as more and more people do just what you've done and you have your faith in humanity restored even in the darkest days.
Welcome to the people's peaceful revolution that is Bitcoin!