Kyderra wrote:any one cares... really?, I mean, look at this
Yes. As you can see, JPG has clearly reduced the quality, while PNG left the picture nice and intact and yet, managed to create smaller size, even when you used lower compression setting. Look, I saved the same picture in PNG with higher compression setting and reduced that 14.5 KB to 9.58 KB with
no quality loss.

9.58 KB (optimized) PNG
Once again, JPG uses cosine transform, which suitable for photos, where are smooth color changes, so it's very effective for them and does not cause such big artifacts. However, this algorithm is not designed for computer graphics, with large solid-color areas and sharp transitions (lines), where it produces visible artifacts and also does not compress it very well, because it's not compressing the type of data it was designed to. PNG on the other hand, is much more suitable for such graphics. It can compress it to very small sizes and yet, it does not remove any data or cause any artifacts. On the other side, it's not very good at compressing photos, because it was not designed to compress them, so it produces larger files than JPG (however, it is being used even for photos, when you need not to lose any data and have the original picture completely intact, like in graphics studios or medicine).
So basically: Why use format which cripples the picture, when there's alternative which stores it at maximum quality and yet, produces (usually, it's not a rule) smaller files than the crippling format? Why intentionally use the worse alternative?
Also look, here's the difference between JPG and PNG, when you XOR the both pictures (you can see which parts the JPG crippled):
