It seems the car audio world should be petitioning and speaking to the automobile manufacturers and engineers to allow for easier integration. This might be way too simplified, but I would think a couple of factory optical outputs and some more flexibility with the factory headunits and aftermarket amps/dsp's would help close the gap between the two.
The industries seem to clash at times with there integration. Some of the car audio tech is stuck in the eighties and new cars are finally taking a step forward in giving people what they are already used to in other parts of there lives. USB, wifi, bluetooth, toslink, voice command etc. Half of the aftermarket audio industry is trying to embrace it, the rest seems to resist it.
I know I'm too much of an optimist at times, but the industries should try to meet more in the middle. Or at least car audio needs to keep up. There is less and less of a reason to have to pull my dash apart to plug 3 fucking wires in, just to get an amp running, instead of having connectability in other places in the vehicle. Its just a turn off with how much work needs to be done, for something pretty simple. Make installation of basic upgrades doable for the average Joe and the hobby will come roaring back. Just a rambling opinion though.