They are likely profitable and because raising cash is comically easy and cheap right now -- would you turn down $600MM in exchange for And when they inevitably
do go public, they'll likely have a very pretty balance sheet, with a massive cash war-chest.
Keep in mind that they are a cash-heavy enterprise -- their risk exposure is any company that uses them goes bankrupt and they're on the hook for all the chargebacks.
Their blog post[0] describes some business that aren't allowed, but provides some insight into their exposure:
> We recognized that the private jet market is different and analyzed financial statements, payment flows, customer profiles, and more to fully understand the underlying mechanics of the business. We modeled OpenJet’s business and determined that the credit exposure was within an acceptable range. We engaged our banking partners with concrete financial analysis, put in controls to monitor risk as the company grows, and OpenJet successfully launched on Stripe.
Let's say OpenJet as an example has ~$10MM of annual revenue. Let's liberally assume people don't book flights out further out than 6 months -- so ~$5MM of annual revenue is up in the air, so to speak. If OpenJet goes bust tomorrow, OpenJet's creditors -- including Stripe -- are on the hook for anywhere from $0 to $5MM of outstanding fares that could get charged back.
That's just one business. From TFA:
> Stripe has ridden the wave of ecommerce growth, with more than 200,000 new companies in Europe signing up to the platform since the start of the pandemic. John Collison said it handled almost 5,000 transaction requests a second in 2020.
How many of these companies will go bust? Even if we assume Stripe is profitable, their losses are surely huge and unpredictable, so having a huge pile of cash helps insulate them against market swings and lets them take bigger risks on bigger, possibly riskier customers, which in turn helps them make even more money.
0: https://stripe.com/blog/why-some-businesses-arent-allowed