Becoming an adult is hard. It can be even harder if you live a sheltered, privileged life. Such as the life of the computer programmer. But to found a successful business, you need to be an adult. Or be sheltered by one (or more).
If you grow up programming, you are privileged: you are intelligent enough to create something complex, useful, and are probably competent enough to get a job whose starting salary is likely twice that of the average person. As an intelligent person, you may believe in a world run by logic and merit. The code either works or doesn't, has bugs or doesn't, looks clean or doesn't. You write good code, you get paid lots of money.
On top of all this, as you write code, you learn that there is a collection of people on the internet who have certain values and principles, and that you are actually using their work, for free, basically out of nothing but good will. This is inspirational, so you decide you will dedicate your life to the same. However, making something for free and giving it away means you can't pay for Mountain Dew. So you decide to make a company, so you can make and give away the code, and still make money.
There's a problem, though. So far you are still thinking like a privileged programmer. But [capitalist] business requires a different mindset. The values and principles of business are not those of the noble engineer. Business values profit, and its principles are based on solving a problem for a customer. But more than anything, business demands the will to compete, at any cost. This is dog-eat-dog. There's no room for generosity, unless you're already winning, and the generosity is ensuring you'll keep winning.
An "Open Source Company" is, by definition, nonsense. It's trying to combine two completely ideologically separate things, having both cakes, and eating them too. Sure, you can have a business that also makes open source. But your business can't be dependent on that open source to make a profit. If it does, then eventually you will have to come out from your shelter and get wet, or you will lose the business, and possibly the code too.
Most of the people in the world don't care about the values and principles of open source. They care about solving the many problems they have every day, so they can feed and shelter their families and still have some leisure time. Most people don't care about your software license. They just want to use a product that makes their life easier. And that's what a business is supposed to do. Open Source is a distraction from that aim. If you really want to solve someone's problem, do that first. Later, once you are very rich and successful, and have many different aspects of the business that generate profit, then you can release your code for free, without it becoming a distraction.
The people who value open source code may not like that your code is closed. But they will respect your honesty, and a product that solves a problem well. And you get to make something you like making, and solve problems, and feed and shelter your family.