Samuel was a chosen disciple of Eli who was the priest of the temple (hekhal)"where the ark of God was". Samuel received an oracle from the Lord, about the God's punishment that will be done to the priesthood family of Eli (for his sons' evil naughty and evil deeds of the temple's cult). Why was this going to be, how God wanted to punished and what lesson God wanted to teach his people?
We found out it in the following story of the ark (chapters 4-6). The Israel's army believing in the magic power of the ark, brings it for the battle with the Philistines who are astonished and feared about the enthusiasm of the Israelites. But the ark didn't help them win and the Philistines took it over and brought to their country. They kept putting it in 6 different cities and every time were forced to move it out because of the Gods plaques sent on their inhabitants. The Philistines seeing the the power of Israel's God stands behind it decided to return the ark and make as well the act of penitence adding the certain amount of gold and other treasures. Finally, after a tricky experiment (chapter 6) the loaded with the ark and the gold cows entered the Israel'a territory welcomed cordially by the people.
The interesting fact points Buber, that the ark "returned to the border town under Israelite control (that the tale has a historical kernel can scarcely be denied), but Samuel, the proclaimer of YHVH who is Himself the vanguard, does not retrieve it."
This can explain why in the following chapter (8) Samuel wants neither the anointed king nor the ark, because according to his concept only YHVH can rules over Israel.
Source: On the Bible, Eighteen Studies by Martin Buber, Syracuse University Press 2000, pg.131-136