If an individual is capable to run a business by themself, then there is no need to bring in a partner because partners can actually complicate business and make a business not to survive in a long term.
If you work in tech, it is almost natural that you will have a business partner. Their term is a co-founder. So while you may be the CEO, your co-founder will be the CTO. You hold the CEO AND CTO position at once. Even when you want to raise funds for your business, you are going to be asked about this. This is what I have learned about the tech field and anyone who have observed this will know that they are mostly two.
Not just in tech but in any business, many business people have a business partner. It's not that they are not capable to run the business on their own but they believe on the saying that two or more is better than one. I'm familiar with the terms that you have given there but I know that they are not limited to that.
Even if the next position is lower than them, I still think that they are qualified to be called as partners and they still play a major role on the success of a business. Each has their own roles and each can be asked depending on what is needed but the CEO or the head of the company can always get asked first or last about it.