Some people are always looking for a free ride. Amassing power/influence/status/assets is usually a way to do that - basically get others to do the hard work and take 5/10/50% of the credit. This appllies under all systems due, most probably, to the natural diversity of humans.

The job of the "system" (legal, political, economic, even cultural and religious) is to mitigate excesses and especially abuses of power before it comes to extremes of bloodshed; but as those also sometimes concentrate power, they themselves need something to regulate the systemic abuses or the non-sytemic abuses of empowered officials.

Humans are the problem, some of them. But greed is also motivational (and sloth), so you can't get rid of it entirely.

If you can keep your society smal enough that basically everyone knows what most other people are up to, it doesn't take much regulation, beyond trust and reputation. But as if your society grows to where some people are effectively faceless and unknown, then it becomes more problematic.