Higher speed optical transducers cost significantly more and there’s no particular standard so interoperability is an issue until enough companies settle on a single standard and a “critical mass” is reached. There’s a set of transducers for 100Mb optical Ethernet that aren’t horribly expensive, perhaps more people will be using them. They can carry multichannel quad rate DSD. For example Merging Technologies recently went to Ethernet connections for all of their new recording and editing equipment. That works very well and you can use copper or fiber to connect the units together.
Jitter is the deviation of the edge signal from it’s ideal point in time. In signal transmission theory (e.g. working with GPS, SONET, high speed Ethernet, etc) jitter is very well understood and people realize it’s something to take seriously. People don’t argue about where it comes from or that it shouldn’t be there: they understand the (many) causes and the (sometimes incontinent) solutions.
In audio people used to deny that it was a problem. These days many people that are used to digital transmissions sending essentially perfect bits don’t see how jitter could affect digital audio. Also non-engineers don’t understand the many sources of jitter. Paul has put up some talks I did about jitter up on the PS Audio DirectStream pages. If you haven’t watched them, please do.
We’ve taken some strides in that most people now accept that jitter can make a difference for audio. But the point I’ve been trying to make for about a nine months here is that everyone’s systems have different sensitivities, RF, groundloops, power line noise, etc. Even if all designers understood all of the pitfalls, the cost would be prohibitive to “harden” each component to RF, jitter, HF noise on the power lines, etc. and it the cost would be prohibitive to make each component a good citizen, i.e. to not radiate, not ad noise to the power lines, etc. For an example most people who incorporate linear power supplies actually add a lot of noise to the power lines because linear power supplies typically take huge gulps of current right at the tops of the AC sine waves. That ends up interfering with the other devices taking big gulps at the same time. With switching power supplies you have the choice of having smoother output power (but adding more noise to the input power) or being nicer to the incoming power (but having more noise on the output power.) You can guess the choices most designers make 
People seem to think that there’s one answer that helps all systems. There isn’t. You need to learn about your system and the things that matter most for your situation. I keep baskets of power cords, interconnects, optical cables, etc. and every time I get a new component I try multiple versions of them till I find what works best: I’m getting pretty good at guessing what I need to do in my system, but I know that that probably doesn’t help most other people.