Because that is huge, no one can mention it.
Just tell me, how many times has Dash doubled it's price since it got released? More than 100
And litecoin? More than 50 too.
Not to mention major altcoins like Ethereum, Monero, Dash, Ripple etc have also grown at their own exponential rates in the year giving a big pump to the overall cryptocurrency market cap.
Bitcoin is probably the only one who increased less times, only that yes, it has an incredible value and probably this is what makes the whole difference with the other altcoins.
But 500 B is a lot of money, i can not wait anymore until it reaches 1 trillion,

Bitcoin was the only coin to start with $0.00000000 value. It has doubled infinity times.