If you have many Bitcoin from a long time ago, you will see the profit grow in your wallet. That profit will be grow more in the future following the Bitcoin price especially when Bitcoin price can increase to the highest price. People who bought Bitcoin from a long time never expected to see that huge profit so they can sell their Bitcoin and enjoy the money.

Let say you have 210-215 Bitcoin, you will see that $13-14 million according to the Bitcoin price now. So I assume that you have 215 Bitcoin in your hand as you say $13-$14 million. But you will not have that huge money if you don't sell your Bitcoin. That profit will be increase in the future following the Bitcoin price.