And we're told "send sRGB" so we are now to assume that this RGB data is somehow magically altered based on what? So I send the same RGB data (numbers) to the device and every time it produces differing results? That would make reprints a bitch.
Actually this is a problem ... these machines have large amounts of drift.
The sRGB data is modified through a lookup table that is constantly being modified to compensate for this drift. In the early days with the Kodak CRT and LED printer, we usually had to tweak the lookup table by hand. I'm sure these have been improved, but I don't think this LUT is as sophisticated as an actual profile, and at this point that process is assuming an sRGB file coming in. It could be the very latest hardware has improved and has found someway to do this via profiles, but that is also challenging. It's hard for a lab to justify spending 100k to 200k to upgrade a printer for this capability, and these printers run for a long time.
We have a test image that is printed at startup of each machine after it is calibrated daily, which is sent to our central lab for monitoring. The drift is apparent and the variation from machine to machine is obvious. When we see one that is too far off we send in the tech. Of course, this drift is nothing new, just goes with the territory of the chemical process, and it usually isn't enough to reject the prints. But it can be a problem if customers compare reprints side by side.
The printer is trying to reproduce the same color and all of this was designed because of the limitations of the silver halide process. It works pretty good, but I've always wondered if because of the large amount of drifting if a color managed workflow as we know it would work, since it would almost require new profiles to be made daily. A few years ago I spent a great deal of time trying to come up with a way to standardize color across all output devices, as we wanted a solution that would allow customer to pick up prints at other locations. Because all of the images are portraits it is very challenging because the expectation is higher than consumer snapshots being produced at places like Costco and Walgreens.
I finally gave up since I sold the company, but never was very successful. As I mentioned, I'm now researching it pretty extensively because of some new projects I'm working on. Hopefully there has been some progress, but even if it has it will take a while to trickle down so it becomes as standard as current inkjet workflows.