Regardless of this (assuming this is even true), I can't imagine that a finance company would want to store their data inside something like Firebase - The risk of data theft is too high and the value of the data is also too high.

When you store everything in a big centralized system, the risk of that data being compromised increases greatly. Right now, the reason why no one is hacking Firebase is because the data which is being stored in there is low-value.

If banks and hospitals started storing data in Firebase, you can be sure that it would attract the attention of hackers and you can be sure that they would find an exploit eventually.

You can't possibly place all of the world's high-value data inside one or two systems. Every single change made to the codebase is a potential security vulnerability.

Also, I imagine that employees of Firebase have access to all your data - What if one of them decided to share your data with a competitor. Humans are corruptable - This is too much power to put in the hands of so few people.