There's a standard tech-nerd bias that assumes that technology will always save us, but just throwing electronics at the problem doesn't necessarily solve anything.
For example, the Army found that using glass cockpits doubled or quadrupled the accident rates in UH-60 and OH-58 aircraft respectively, increased it by ~30% in the AH-64, and reduced it by ~40% in the CH-47.
http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=ht...
http://www.usaarl.army.mil/TechReports/2001-12.PDF
A five-year NTSB study found that although glass cockpits had twice the incidence rate of fatal accidents. The study concluded that glass cockpits do not show a safety benefit. This remains the position of the NTSB.
http://www.ntsb.gov/safety/safety-studies/Documents/SS1001.p...
http://www.ntsb.gov/news/events/Documents/2010_Glass_Cockpit...
http://www.ntsb.gov/safety/safety-recs/recletters/A-10-036-0...
The reality is that simpler is sometimes better. Mechanical instruments each do one thing and they do it well. Vacuum-driven systems are simple and extremely reliable. You cannot fly a 100% glass cockpit, period.
What glass cockpits really do well is information integration. That makes it easier to surface relevant information for the pilot but it also means that pilots have to handle more complex systems that are throwing more information at them, and yet also may not be throwing the right information at them.
This is an inherently one-way street, the reason we have the instruments we do is because they're relevant, you can't go hiding relevant information from the pilot. As such, NASA recgonizes that glass cockpits and cockpit automation impose a higher cognitive load on pilots. It's very simple and straightforward to interact with a traditional cockpit, but with a more advanced cockpit you also need to have a correct mental model of what's happening in the background, otherwise "cognitive mismatch" will result.
Just like any other abstraction - it's nice when they work but all abstractions are "leaky" to some degree or other and you need to know how it works and be able to route around the problem to fix the cases where it fails.
The long and short here is that experience and frequent training are the key factors in aviation safety and glass cockpits actually increase the requirements in this area. They're nice when they work but they certainly are no panacea.
http://human-factors.arc.nasa.gov/flightcognition/research/s...
https://www.thinkmind.org/download.php?articleid=achi_2012_1...