If you keep track of what people now have as high score, resetting the score will not have much of value, because people are tempted to either not do their best, or if they just were lucky getting that hich score, and cannot do it again, they just will say: oh, but I don't mind. I already have a very high score, see other score table. Try beating that. Which basically is the same as not resetting the scores, with exception that in this case your score gets recorded.
But it gives way more trouble to create another score and maintaining it.
EDIT: I'll give an example:
On a game, I somehow managed to get a score of 482, while everyone else seems to have a score max of 479 because of some glitch I got a higher score. I now cannot get higher than 479 anymore, so I say: oh well... I still have the best score because I once got 482, see other score table.
Or another example: I once got a score of 539158315 and spent hours on getting that score. The scores are being reset, and the highest score now is 534246. I try but due to not being focussed enough, I just can't beat that score. I say: oh well, I once had this enormous score, so try and beat that!
Poll
)