There are some advantages to JPG. For example, in casual Hidden Object games that have lots of full screen backgrounds, huge "sprites" etc. it's sensible to use JPG. In fact almost all casual frameworks support it.
Sometimes is acceptable to have slightly lossy images but with the benefit of much smaller game download. JPG at 95% quality is still way smaller than PNG, without apparent degradation in quality.
Also, textures for 3d models mostly don't have to be losless, due to the way they're displayed on screen.