Why does launch only appear like twice in dragonball z?

Cause she is unimportant.

that is because they made her unimportant. They could have easily given her significance. Or at least comedy relief.

yeah launch wasn’t a very well developed character, i don’t remember much about her other than that. sorry> i imagine that the reason she showed up so little in dragon ball Z is probably because i believe dragonball was done after dragonballz. so they couldn’t have made her a more important character since she didn’t exist until dragonball came out