Sure, the why of reviewers don't benching multiplayer is well known: hard work and not easily repeatable.

But multiplayer BF is a very popular game and going back to Mantle (and more recently DX12) reviewers have done a very poor job. Benching BF4 Mantle with a highly overclocked HEDT system, playing single player and then proclaiming that it makes almost no difference is not a useful benchmark. Equally, benching BF1 single player in the recent Ryzen reviews and finding that the Kabylake i7 is faster is not that useful a benchmark, when BF1 multiplayer can saturate all the cores of an i7-7700K at times.

And to me, a £300+ CPU is niche and the ones spending so much on a CPU might reasonable expect to be able to stream while playing their mulitplayer BF1 matches and that's where a Kabylake 4C/8T may not cope and they'll have to spend even more on Intel HEDT or buy a Ryzen.