It would be far easier to force phone and camera manufacturers to “embed” a fingerprint in the photo than to measure every sensor.
Also these fingerprints in reality are very flaky and the higher the quality of the sensor the less of a fingerprint there is to work with.
The fingerprints are also dependent on specific operating conditions which can change with firmware and operating parameters (e.g. digital zoom / cropping) as well as environmental conditions such as light levels and even temperature.
Most phones do that for you anyhow. Unless there are serious defects in the sensor that would probably mean it would fail QA even for bargain bin phones the amount of “AI” post processing that phones do these days is probably sufficient to erase any sensor fingerprint.
Even with DSLRs and RAW files you often don’t get a RAW output from the sensor all of them do their own “color science” magic and other alterations like denoising too even on the rawest of the RAW settings.
RAW files today just mean that the files are uncompressed or the least compressed since there might be some compression/downsampling happening at readout anyhow and that you get a ton of metadata that can be used by a photo editing app to better work with the image.
The file, but not the image. Also easily removable, although companies have been clearly encouraged to make this difficult in mainstream software and to set maximal defaults. Probably doesn't take much encouragement, because the more metadata, the more automagic.
Also these fingerprints in reality are very flaky and the higher the quality of the sensor the less of a fingerprint there is to work with.
The fingerprints are also dependent on specific operating conditions which can change with firmware and operating parameters (e.g. digital zoom / cropping) as well as environmental conditions such as light levels and even temperature.