Bitcoin (BTC -1.35%) keeps proving the skeptics wrong. As of July 31, the world's leading digital asset has soared 27% just in 2025. This continues a fantastic long-term streak, with Bitcoin now trading close to its all-time highs.

There are certainly investors out there that have missed the boat. And seeing this cryptocurrency's price appreciate so much in the past can discourage them from jumping in the waters. But there's still meaningful upside, in my view. Here's one reason why now is the time to buy Bitcoin.

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Scarcity is the most important characteristic

In the past year-and-a-half, Bitcoin has really grown up. The Securities and Exchange Commission approved spot ETFs in January 2024. The White House created a Strategic Bitcoin Reserve. Banks are now allowed to custody the crypto on behalf of clients. And the financial ecosystem supporting Bitcoin continues to expand.

While these catalysts legitimize Bitcoin, it's not the top reason to buy. Investors should seriously consider adding Bitcoin to their portfolios because of its scarcity. There will only ever be 21 million units in circulation. That limit is written in the Bitcoin software. And it is unlikely to ever be altered.

Growing fiat money supply

The U.S. federal debt balance sits at $37 trillion. This figure, as well as the country's money supply, have exploded higher since the Great Recession. And there is no end in sight to this financial mismanagement. Even noted entrepreneur Elon Musk couldn't really do much with the Department of Government Efficiency initiative to cut spending.

Bitcoin's thesis is simple, highlighting the difference between unlimited fiat currency and a limited supply of the digital asset. As long as the government continues to take on more debt and grow the money supply, Bitcoin's price should keep going up.