At least with regards with the fintech industry, due to the myriad regulations one must pass to do most things, securing a large customer is sometimes the only way to survive, let alone enter the market. One of the main reasons we haven't been exposed to as many large startups in the space.
The best example of this is Bloomberg. The first 20 terminals went to Merrill Lynch (https://www.fastcompany.com/3051883/the-bloomberg-terminal). In fintech, I think both the regulatory hurdle you mention, in addition to solving semi-custom workflows can be a prerequisite for developing a useful product. Take Addepar for example. They have to integrate into the Bloomberg's of the world before they are useful. And, while specifically, a Bloomberg integration could be meaningless for the next customer who uses Capital IQ, neither are likely one-off integrations. Spending time customizing/connecting to other smaller/startup fintech services probably is likely disastrous.
