Because we recognize that we were evil and want to make amends.
'Wiping the slate clean' is a noble path to peace when both sides have done something wrong; it is a far less noble idea when the injustice was severely one-sided, instead it can actually make the injustice worse.
Suppose someone had -unprovoked- attacked you violently and and taken your home and possessions, and then moved his family into what used to be your home. Then suppose his family, still living in that house and intending to continue doing so, suddenly proposed 'wiping the slate clean'. Would you be right in suspecting their proposal of 'wiping the slate clean' to be in this case completely self-serving?
https://en.m.wikipedia.org/wiki/Cherokee
It also begs the question: What are the Romans and the Arabs going to give my country in return for having conquered us 2000 and 1000 years ago, respectively.
White colonists have had the upper hand for a few centuries now. It's undeniable that some indigenous groups are still actively suffering from the colonial occupation in the USA. Any and all attempts to help level the playing field are laudable.
If you feel like you are currently underserved by your state as a result of the Roman / Arabic occupation of your state then I hope you too are seeking to redress the balance.
Chereokee were oppressing the other tribes before the arrival of the Europeans and then fighting along the Europeans in order to dominate other tribes.