Xmastime, Lawyer for Hire!!

The Curb Your Enthusiasm finale coupled with it reminding us all of the Seinfeld finale begs a more serous question; should it be, or WHY should it be legal to base the decisions of a court case on previous events, some of them years & decades earlier, or should it (theoretically, at least) only be allowed to be decided based on the actual events of the current case? 🤔🤷‍♂️