My gut feeling is that memory bandwidth has been left to the wayside the past few years of hardware development. It’s obviously an important factor for server deployments, but the majority of the breakthroughs in the memory space has been on miniaturization and power efficiencies for usage in tablets and laptops. And let’s face it: You don’t really need that much bandwidth to watch Netflix and browse Facebook, so there’s not much incentive to work on throughput for most hardware manufacturers.
Getting some raw numbers on the current situation is a good starting point on how limiting this aspect of current hardware can be. It also illustrates why being able to scale horizontally is an important factor as throwing more resources at the problem won’t get around this bottleneck. I also know of a few simulation games that are suffering from memory bandwidth issues, so I doubt this issue is limited to servers or just framerate in shooter games.