Why don't many people use PNG image files on webpages compared to jpeg or gif?

[froggyboy604]

I think because the creaters of PNG did not promote png much, so people still use jpeg and gif for web graphics because they don't know about the PNG image format.

Plus, some mp4 players, or digital frams, PMP, etc only support JPEG and Gif.

Similar to how many people use wav, wma, & mp3, but not so many people use OGG.