Because…
> the legacy of slavery has left significant and enduring socio-economic disparities between descendants of enslaved people and those who are not. Inequalities in wealth, education, health, and opportunities persist, often along racial lines. These disparities aren't merely coincidental, but have been reinforced by racially discriminatory policies and practices like segregation, redlining, and racial violence, all of which have historical roots in the institution of slavery.
Parent made the case very plain.
Try a thought experiment: your ancestors were enslaved in America. After emancipation, every generation of your ancestors was subject to both systemic and individual discrimination and violence.
The question is, what would you want done? Do the answers “well that’s all in the past” or “how about these other people though” satisfy? It’s worth thinking about. Personally I do not know what my own answer would be, other than that I would almost certainly be angry and distrustful.
I can certainly understand why one would be bitter about "every generation of your ancestors was subject to both systemic and individual discrimination and violence". They have a right to be upset. A lot of people have a right to be upset about a lot of things. I don't think you can jump from that to reparations though.