The fact that they don't currently doesn't mean they can't very soon. Do you ever use Live View? I'm still unpersuaded that, aside from battery life, there are any serious problems with EVF that can't be overcome in a very few years. And, when that happens, EVF will be indisputably superior to OVF.
Sorry, EVFs don't show that, they show the in-camera JPEG conversion, which is way, way smaller than what the sensor can see. I post this example often:
I have a pair of the Olympus "tough" waterproof cameras... One is about 4 years old and the other is last years model. A friend just bought the latest version. On the 4 year old one, lag is very noticeable and the viewfinder sucks in poor light. On the one year old one, lag is not noticeable and the viewfinder is noisy in poor light. On the new one, there is no noticeable lag and the viewfinder is close to what the eye sees in poor light.
This is the march of progress. Just using this as an example, four years ago I would have said that EVFs are a long way off, but today I would say that they are close..... and this is with a cheap P/S camera. The viewfinder in the OMD EM-1 is superior to this EVF... and what is coming down the pipes? What do Canon/Nikon/Sony have planned for the future?
Ever use liveview on your DSLR? Ever zoom in 10X to check the focus? This is a trivial problem for an EVF, yet impossible for an OVF.... you have the option to switch between what the sensor sees and processed views....
And now lets travel back in time to the origins of the SLR camera... it was an ingenious design that allowed the eye to see the light that would be presented to the film. A DSLR with an OVF is the same, it allows your eye to see the light that is presented to the sensor. An EVF goes one step further and allows you to see the light as viewed by the sensor.
New cameras have ten times or more computing power than those of just a couple years ago... they can do complex noise correction on the fly.... the on-the-screen jpg of four years ago is not the same as it is today. You can not use the inadequacies of the past to justify the future.