I have read the odds are about 4-1 or 80%-20% in favour of the overpair e.g. AA KK or even 33 22 but why statistically isnt it 51%-49%.

Because with both pairs drawing five cards isnt it 50-50 whether either will make a set and the extra percent indicating that the overpair will win if nothing hits?

It's not going to make my world crash down but I was just looking over odds and thought it was a little odd, whenever I throw down an overpair like QQ JJ I certainley dont feel like a big favourite lol.

forgive the n00b for his stupidity