You want to make software that adds value either way. But this way the value is directly generated for your employer, with no customer in the middle.
I'm not saying that eliminates other influences, certainly I think (and have heard) this leads to workplaces dominated by strong and often eccentric personalities, which has its downsides.
But insofar as a programmer is motivated by creating value, and by value we mean money here, I can't think of a way to be closer to it without being independent.
The personality cliché in finance is the risk taking one. Men are more frequently found in riskier professions, including dangerous jobs like oil drilling.
Some fintech companies actually do produce a software product for finance. However, many of them work for banks or funds to generate capital gains beyond a wage or salary.
Regardless of personalities, the most important factor is profit. Everything else is secondary. It is not as flashy or famous as big tech companies, but this profit is paid in bonuses that far exceed the highest salaries for tech workers.
If you work for Netflix, maybe you get a free subscription. If you work for a restaurant, maybe you get a free box of takeout at the end of the day. If you work in the business of money, your incentive is large bonuses.
Can you recommend any sources (blogs, whatever) for info on what it's like to work at such places?
I've always found it intriguing but I'm not sure if I have the right personality or skills or (very complicated) geography to make it worth trying.
Depends a bit on what part of fintech you are working on.
There's lots of rank-and-file employees whose good salaries actually mostly depends on competition from tech companies. With a low-risk lifestyle mostly comparable to said tech companies.
To get the crazy bonuses, you need to move closer to the traders and some of the quants (or get very lucky). But generally those people work a lot harder and longer.
I've worked in tech companies (like Google and Facebook) and in those low-risk fintech roles (at eg Bloomberg and Goldman).
It seems that the finance industry as a whole seems to be moving away from the heroic model with enormous bonuses to the tech company model with good salaries.
The latter is cheaper and more predictable, and it fits the organisations as more and more work becomes automated.
(That observation is about companies like eg Goldman and only meant to capture an average. They still have plenty of individuals pulling heroics; and there are still plenty of hedge funds and similar on the old model.)
As another example, take high frequency trading market makers. They generally don't have any human traders at all, because humans would be way too slow. So their very nature forces them to become closer to tech companies in organisation.