Bebop's episode nature is what makes it so amazing. If it focused almost solely on Spike's past like you wish it had, it wouldn't have been half as memorable or enjoyable. Spike is fucking awesome, he's one of my favorite characters, but the point was he was trying to AVOID HIS PAST. THE ENTIRE POINT OF THE ANIME IS THAT YOUR PAST IS NOT SOMETHING YOU CAN RUN AWAY FROM. IT WILL CATCH UP TO YOU. YOU CAN ONLY GET AWAY FROM IT FOR SO LONG.
In the mean time, let's take a look at the heartache and tragedy that is common to all of mankind. It is not exclusive to Spike. That is the beauty of Bebop. His story is just one of the more grandiose and tragic of the many other tragedies that befall people regularly in this rough and tumble galaxy.