Do you want to run the country? Do you think you have the time to run every aspect of the country? If you don't, then you need to delegate the authority to run those things to others. And then the people who are doing those jobs become the rulers in those areas.
And those areas are going to have to work together, at which point you get hierarchies and people similar to managers and fairly rapidly you end up with what we'd call a government.
If you believe there's a better way to run things, then start a company that works in a more egalitarian manner and scale it. As I understand it though, companies that work even vaguely like that have never scaled well beyond a few hundred people at most - i.e. Dunbar's number.
If you want to solve the problem of people needing a government there are serious questions about complexity and conscientiousness (do people even want to run their own affairs?) and how people are meant to work together when they can't know everything about all the areas they'd have to oversee without empowering others even if they just did that as their full time job.
So, my answer to why do I think people need rulers is, essentially, that equality doesn't seem to scale well to the sorts of problems that a country would have to address at the moment - and, implicitly, that anywhere that decides not to be a country anymore is going to get walked all over by anyone that decides to still be a country.