What i don't understand is why are camera companies so damn stuck on jpeg? it's just an all-around lousy format. PNG is way better on every level. It can be compressed similarly to jpeg, can be left uncompressed, supports 16bit file formats and is an open format (i think). It's all around more suitable for about every application.
PNG gets around 9:1 compression for an average image.
JPEG can get up to 100:1 compression for an average image if aggressively compressing or if the image is not too busy, and around 20:1 even at higher settings and busier images
Also, jpeg is specifically designed for naturalistic images like photos. It cuts corners in the places that are most logical to cut corners, based on human perception of images. So even though it has higher compression that begins to enter into the lossy realm, the losses are the ones that matter least for what photographers care about. PNG is lossless, so it isn't making any of those corner cuts that we can and frankly should get away with if looking for an immediate, SOOC export format.
PNGs would not really add anything useful. They would accomplish less compression, AND do so only for the sake of retaining information that your eye doesn't see very well anyway, which is pretty silly and unnecessarily clogs up hard drives and servers. Also, it wouldn't offer a sliding scale of reasonable->high compression based on preferences in the moment, like jpeg does.
Finally, PNGs are not compatible on quite as many devices and programs as jpegs are. And some programs or websites, even if they accept PNGs, will simply turn them into jpegs anyway before using or posting them (like facebook, in order to save on storage space due to higher compression of jpegs), so if you edit a PNG to look the way you want, you won't get the results you expect when uploading, unlike a jpeg at the right compression.
For the DSLR world, PNG would just be a less useful attempt to fill a niche that jpeg already fills better for SOOC, decent looking shots that take up minimal space. Nor does it replace RAW, because PNGs are only 8 bit (still have to throw out RAW data to get there, just like before converting to jpeg) or 16-24 bit (unnecessarily large and storing a bunch of 0s you don't need). Plus, camera companies can't store as much weird metedata in PNGs like they can in their own RAWs.
PNGs are best for storing very small things like avatars or logos, etc. where you might as well have crispness at the cost of only very minor extra storage space due to small size. They're not good for photo storage.