Square (SQ 16.13%) faced a big challenge in 2020 and it stepped up and absolutely crushed it. While its seller business faced headwinds from the coronavirus pandemic, its Cash App business saw soaring engagement and the gross profit growth that comes along with it. This year has the potential to provide more of the same for Cash App while the seller business recovers, leaving more room for the stock price to climb despite its 248% price increase in 2020.

Here are five reasons to remain optimistic about Square.

1. Additional stimulus and tax refunds

Square typically sees increased Cash App sign-ups and engagement during tax refund season, and it noticed similar behavior last year when the government issued stimulus checks to Americans. During the company's second-quarter earnings call CFO Amrita Ahuja said the stimulus benefited customer acquisition, customer engagement, and volume of transactions on Cash App. That led to a 200% increase in gross profit for Cash App in July.

A person inserting a Cash Card debit card into a Square card reader..

Image source: Square.

The government sent out a new small round of stimulus checks in January, and it's planning to distribute larger checks in the near future. Additionally, we're entering tax return season. The two could help Square sustain its Cash App growth from last year as more households adopt Cash App and direct deposit as a faster and less expensive way to access their money.

Deutsche Bank cited stimulus payments as one reason for recently upgrading the stock.

2. Broad adoption of investing in Cash App

Square rolled out its Invest product at the end of 2019. It saw excellent traction in 2020. Management said it was the fastest-growing product it's launched in Cash App, attracting 2.5 million users in less than a year.

But Cash App may have gotten a boost earlier this year when traders became frustrated with Robinhood amid the GameStop stock trading frenzy. When Robinhood restricted trading, about 40% of traders abandoning the app switched to Cash App, according to data from Mizuho Securities. And while traders that abandoned Robinhood are expected to trickle back, 75% of new Cash App users were also attracted to other products like Cash Card. That means they're more likely to stick around than those that left for other trading platforms.

3. Bitcoin continues to gain appeal

Square started testing Bitcoin (BTC 0.30%) trading in late 2017, making it available to all Cash App users in 2018. It's continued to invest in the cryptocurrency, both from a product standpoint and financially. The company announced the purchase of $50 million worth of Bitcoin in October. (That stash is worth about $222 million at Tuesday's Bitcoin price of approximately $47,184.)

As Bitcoin has seen a run-up in price, it's garnered increased media coverage, and for the first time, institutional investors are taking a serious look at the cryptocurrency. That lends legitimacy to the idea of Bitcoin as an investment and supported stronger adoption among retail investors. 

Cash App is one of the easiest ways for investors to buy Bitcoin, as it's not offered by most standard brokerages. Square has also encouraged its users to explore Bitcoin investing by offering cash back in Bitcoin as a Boost on its Cash Card. The broader ecosystem gives it an advantage to onboard more users to its Bitcoin investing product.

4. The economy will reopen and small businesses will recover

Let's not forget Square's original business, the seller business, which still accounted for over half of Square's gross profit in the third quarter despite Cash App's booming growth.

There are signs Square's seller services will come back strong in 2021 or 2022, as the economy reopens and people return to bars, restaurants, and live events where Square has a strong presence. In the meantime, Square has made substantial progress getting merchants to use its online platform to build websites and accept payments online. Online gross payment volume grew 50% year over year in the third quarter. Merchants coming on board in the third quarter were tracking higher payment volume than their prior-year cohort, thanks in large part to their adoption of online payments.

That bodes well for the strength of Square's seller ecosystem as merchants look to keep the benefits of online transactions while adding back in-store sales. Square proved it has one of the better solutions for omnichannel sales.

5. A massive addressable market

Square's management shared an update of how it views the business last March. Most telling is the addressable market opportunity. For its seller ecosystem, Square sees $85 billion in potential sales among its current products, expanding to $100 billion when factoring in its potential product expansion plans. For Cash App, there's a $60 billion opportunity. Importantly, these are only in markets Square currently operates.

So far, Square says it's captured 3% of the seller market and 2% of the consumer market, leaving lots of room for growth. In 2021, Square will again take market share, as consumers are attracted to new products in Cash App and sellers use more of Square's tools as shoppers return to stores and eateries.

Strong user growth, payment volume growth, and gross-profit and EBITDA growth should give investors the confidence to continue bidding up the fintech stock.