My reaction is the opposite. I always felt disappointed by how primitive the optical view finder on modern cameras is versus electronic ones. It doesn't get the light levels right and it can barely show you any relevant information; there needs to be a separate 7-segment display on the body showing pertinent information. How primitive!
EVFs, on the contrast, show you everything you need to know right in the viewfinder (including advanced features like histograms, zebra stripes, etc., that an optical viewfinder could never possibly do).
The big advantage of EVFs is that it can do so much more than an optical viewfinder. You can enlarge it, display focus peaking, but most of all, you get a preview of the image you would take - especially previewing the exposure is very helpful. And of course, if you want to do video, the viewfinder of a SLR wouldn't be usable at all.
As far as I know Nikon started off making Contax clones, not Leica clones. Canon did Leica clones, though. Keep in mind that Leicas up until the M3 didn't have a combined viewfinder/rangefinder. That was an innovation from Zeiss first used in the Contax II.
And there's been quite a few SLRs before the Nikon F, it was just Nikon that made it so solid and efficient that made professional photographers switch from using a rangefinder to SLR.
Those were introduced in 1930s and 1950s respectively. Since the launch of Nikon F in 1959 until some time in 2010s the viewfinder technology didn't change. Means shutter became metal and electronic, autofocus invented, man went to the Moon and back, digital CCD/CMOS photography came around, Sun goes down but mirror and prism SLR technology of 1950s just kept on.
One of the reasons why mirrorless didn't appear sooner is because LCDs or OLEDs viewfinder suck(ed). They used to be in SVGA or XGA resolutions, refresh at 30-60Hz or less, few hundreds ms late, dim, power hungry and whatnot. Wasn't so advantageous in terms of weight or cost as well. Optical quality of SLR viewfinder never disappointed its users on the other hand. It is and always had been a joy to be able to just look into it and see through the lens, especially when films take hours to develop.
Sony, however, knew that no one uses viewfinder in a point and shoot digital cameras, or no one has any problems without SLR viewfinder in video cameras, dad on holidays and professional broadcasters alike. So after they merged camera division from Konica Minolta in 2006, they just walked out and spoke out the obvious. Camera nerds were shocked, I was shocked, so were Nikon and Canon. Leica may have been laughing, Zeiss was happy collecting licensing fees. I was skeptical, and I could verify it feels very disappointing looking into EVF. But Sony knew it ain't a problem and it wasn't.
Nikon and Canon probably thought the quality of EVF never satisfies professional photographers, from their narrow expertise.