The E-Myth Revisited, M. Gerber, has some good examples of why it's like that. The thing is when you blur roles, you also blur responsibility.
Organizational charts are like software architecture. In fact, architecture is a subset of org charts. It shows what you're optimizing for. Are you an e-commerce company? Your org chart will have a lot more focus on logistics and payment than a SaaS. Whereas a SaaS will focus more on security and software infrastructure.
You can have a person in multiple roles, e.g. Bob is responsible for HR, finance, and is the mobile lead.
At the seed stage, your goal is to find the business model. So you can have blurry "co-founder" roles for everyone. However someone has to be responsible for fundraising, audits, legal, pitching. Everyone should be able to pitch but someone has to be rehearsing/rewriting the pitch 4 hours/day. So you probably need a CEO.
If you're above seed stage, you are scaling. If you're scaling, you have a business model. If you have a business model that you're committing in stone, you need an org chart. This can be modified later, but well, you should know how much of your resources go into marketing and how much goes into engineering.
Maybe you guys are really responsible and close friends and can distribute that properly. I hear Airbnb was like that. But just be aware why it's a red flag.
Even in games, the positions are demarcated. Some people play forward. Someone in the guild handles research. Someone plays the sniper, not the whole team. So the other worry is that everyone is breaking position and doing engineering and nobody is paying the bills.