Up thru the 900 series, well over half our gaming builds we did for users were SLI ... with 95% at least "SLI ready". SLIs problem had more to do with nVidia than customers .... and nVidia's problem was this ... two 970s were the same price as a 980. And it had no downside. For most games, yoiu say a 70% average increase in FPS, on the games that matters, many were over 95%. That 70% gave yu 40% more frames than the 980. In the few popular games that did not support it, you lost maybe 12% in fps... weighing one against the other it was an easy decision. The problem for nVidia was, they make more money selling one 980 than they do twin 970s... even more so when game bundles are involved. With the 700, 600 and 500 series, the dollars favored SLI even more.
With the 10xx series, nvida made it harder. For reasons never explained, SLI average scaling at 1080p was only 18% ... @ 1440p, about 30%. Yet for some reason, at 2160p it was well over 55% with some games scaling near 100%. Looking at the numbers, it does seem off that the proce equartion was no longer valid at 1080p and 1440p where the top tier card was now keeping ya well above 60 fps. But where it couldn't, SLI managed to make sense at 2160p. With thr 4k HDR panels about to drop at $1,999 or so... they will be too high priced for mainstream users and i don't see a chnage in the parigm until these things drop into the range of affordability. But as monitor technology improvements continue to bring us more pixels, I don't see nVidia abandoning a multi GPU option at the high end.
