(one last try)...
No, it is not rare, in fact it is almost universal. I've never used a DSLR with 16 bit raw files (perhaps they exist, but they would be rare).
Many of the cameras used all the time by many Pixinsight users have 12 or 14 bit native output resolution. This is not rare; is is being handled by thousands of users every day.
Many users will use capture software to control their cameras (and other equipment). I use APT, but there are several alternatives. This software will usually output the image data, not in camera raw files, but in FITS format files, and will usually convert it to 16 bit integer resolution (by which I mean simply multiply the camera raw data by 4).
If you manually download raw files from your camera, you can load them into PI using raw format. In spite of some of the posts above, I don't believe there is any setting in the format explorer interface to request conversion of 14 bit raw input into 16-bit scaling. Certainly, when I read in my Canon CR2 14 bit raw files, they end up with the maximum value of 0.25, just like your files.
I have not noted before at what point PI normalizes these files. I one workflow I examined, it happened after registration; it will certainly happen after ImageIntegration. After normalization the maximum value will be ~1.0. If you really need to normalize earlier than this you can do it youself, but I've never needed to do it (and it looks as though the many many other PI users with 12 and 14 bit cameras manage without it too).
