Dont know either, it wasnt the first time a main character died.
Yamcha's first death in DBZ is memorable because, that is the first time within the main series that someone had died a second time. Prior to Yamcha's death everyone else who has died up til then had only died the once, and each time they had successfully been wished back.
As Goku told Krillin before he went off with Piccolo to defeat Radditz, Shenron would only grant a specific wish (bringing a specific person back to life) ONCE. This is why when they wished the people who Frieza or Frieza's men killed on Namek back to life, Krillin was not returned to life, because he had already been restored to life by Shenron once before. That was the entire reason for going to Namek in order to search for the Dragonballs in the first place, (that and the fact that they needed to Wish Piccolo back to life to use Earth's Dragonballs). Because only the Namekian Dragon could wish people back to life who had already been wished to life once before by Shenron.
