Question re LCD finder refresh speed

I used to own a Sony R1 and often found the refresh speed of the eye-level viewfinder a hindrance. I often continue to read the same objection for more recent camera models. It seems to be a common objection against replacing optical viewfinders, especially for action and sport. But even the lowliest consumer camcorders handle screen refresh pretty well, to my eyes, and have done so for years now. This may be a stupid question but what prevents that technology from being put into DSLRs or digicams? Or has it already? I have not used a DLSR model that also shoots video.