In less than a week, investors can pop the champagne corks and celebrate another successful year. Through Dec. 22, the widely followed S&P 500 was higher by 25%, which more than doubles up its average annual total return of around 11%, including dividends, since the beginning of 1980.

But it's the cryptocurrency space that's delivered the juiciest gains of all. Since the year began, the aggregate value of all digital currencies came close to tripling. Not surprisingly, Bitcoin (BTC 2.89%) has been one of the biggest contributors to this nominal value increase, with a year-to-date gain of 67%. It accounts for 40.5% of the entire $2.27 trillion cryptocurrency market.

A gold-colored physical Bitcoin stood on its side.

Image source: Getty Images.

Bitcoin more than doubled up the S&P 500 gains in 2021

Bitcoin's gains, which recently reached as high as 8,000,000,000% from where it began trading in early July 2010, have come on the heels of numerous catalysts.

To begin with, Bitcoin's first-mover advantage has made it the most-popular cryptocurrency with retailers. As of late 2020, small-business financing platform Fundera estimated that 15,174 businesses worldwide accepted Bitcoin as payment -- and this figure has assuredly grown since.

To build on the above point, Bitcoin was also recognized by El Salvador as legal tender in September. It's the first country to allow Bitcoin to be used as accepted currency, and could pave a path for other nations to follow.

The world's most valuable digital currency has benefited from rapidly rising inflation in the U.S. and abroad as well. Since Bitcoin has a perceived cap of 21 million tokens, it's viewed as an inflationary hedge against a rapidly growing U.S. money supply and price hikes. In November, the Consumer Price Index for All Urban Consumers jumped 6.8% in the U.S., marking the biggest year-over-year jump in 39 years.

Investors look to be clearly excited about the upgrade potential for Bitcoin, too. In November, the long-awaited Taproot upgrade took effect. Taproot allows for smart-contract transactions to occur on the network, which opens the door for a broader use of the Bitcoin blockchain. Smart contracts are protocols that help to verify, enforce, and facilitate a contract between two parties.

Lastly, even the fear of missing out (or FOMO) has played a role. After watching Bitcoin gain 8 billion percent, crypto investors appear to be more than willing to overlook any threat of a reversion.

A businessperson putting their hands up, as if to say, no thanks.

Image source: Getty Images.

I'm still not buying Bitcoin, and you shouldn't, either

Although Bitcoin has proved me wrong over the past year, I still wouldn't buy the most-popular digital currency on the planet with free money -- and I'd suggest others avoid it, too. Below are some of the reasons I simply can't buy into the hype surrounding Bitcoin.

For starters, it isn't the scarce token it's made out to be. Take gold as a comparison. Since we can't use alchemy to make any additional gold, what remains in the ground and what's been already mined is all there will ever be. In terms of physical scarcity, that's a true line in the sand. As for Bitcoin, lines of code are what limit its "cap" of 21 million coins. Even though consensus is unlikely to increase the number of outstanding tokens above 21 million, it's not impossible that it happens. Thus, Bitcoin only offers the perception of scarcity and not true scarcity.

Another big issue for Bitcoin is dilution. But I'm not talking about the modest coin inflation that comes with cryptocurrency mining. Rather, I'm alluding to Bitcoin being a first-generation blockchain network that's being left in the dust by third-generation blockchain innovation. There's absolutely no reason for Bitcoin to be worth $913 billion when blockchain projects at a fraction of its value can scale better, process faster, and handle far more complex transactions. Bitcoin may be benefiting from a first-mover advantage, but the first to the foray is rarely the victor.

A visibly worried person looking at a rapidly rising then plunging crypto chart on a tablet.

Image source: Getty Images.

History provides yet another reason I want nothing to do with Bitcoin. Major price swings are somewhat commonplace in the crypto space, and reversions following huge gains happen often. Bitcoin was up 8 billion percent at one point since July 2010 and has yet to demonstrate that it truly has staying power. Since it's been unable to decouple from the stock market, I would be betting on a significant reversion following its pandemic-low bounce.

To build on this previous point, there now are considerably more avenues to bet against Bitcoin than there have ever been. The rise of Bitcoin-focused exchange-traded funds and Bitcoin futures offers a safer way for big-money players to bet on downside in the world's most-popular crypto. In other words, Bitcoin becoming more mainstream as an investment will hurt more than help.

And finally, history also tells us that investors have a really poor track record of estimating the adoption of next-big-thing technologies. Looking back on the internet, business-to-business commerce, genomics, 3D printing, and so many next-big-thing advancements reveals that their adoption took far longer than expected. This isn't to say that blockchain can't become a mainstream technology in payment and nonfinancial applications at some point in the future. But it's important to recognize that businesses aren't willing to jump at the chance to use blockchain until it's been thoroughly vetted in the real world. We're just not anywhere close to that yet.

There are plenty of cryptocurrency projects that are really intriguing and could change the course of payment processing or supply chain management. Bitcoin just isn't one of them.