It's simple. If the system requires change, who is going to bring it? Those who are comfortable in it? Or those who are hurt by it? The answer is obvious. The ones with comfort lose nothing if change doesn't come. Ones without it stand to lose even more if things don't change.
So the question "why do they have to protest?" only comes from those who benefit from the system as it exists right now. The reason they don't see the need for opposition is that the system isn't broken in their eyes. Because it works for them. They don't even see the problems when the problems are specifically pointed out to them. Their frames of reference are so different that they are literally unable to understand how the lived experience of someone else might be different from theirs.
As far as they are concerned, theirs is the only way of life and the only lens through which to see the world. This is why we see privileged folk ask questions like "Why do only they protest?" and "Why don't you see us civilised people on the roads?" The answer of course is that what they think of as civilised is only privilege. And because they don't understand this answer (because privilege only makes sense in context and they have no context except the context of their own life experience), they fall for the dehumanising answers.
Answers like "these people are uncivilised by nature" or "it's in their blood only". And thus starts the process of the privileged high-fiving each other over their "logic" and "realism". In truth, theirs is a child's understanding of the world. And like a child's worldview, it is extremely confident. Unfortunately, unlike a child's view of the world, this one can end up causing a lot of real-world damage.
When this childish privilege is unleashed into the spheres of policymaking, we get discriminatory laws, lapdog media, and hate-mongering politicians calling for murder from stages, all of which happens while the privileged nod from their drawing rooms and their dinner tables asking "that's exactly what needs to happen" and "these people should be put in jail" or "these people should be shot" or "these people are attacking us".
The journey from smug child to scared child is a short one. The future, if it's going to be different from the past and the future, is not going to be brought about by sitting on our asses, blaming peaceful protesters for violent crimes, and not making any efforts to understand how the other half lives.