It's because 99.9999999% of all reviewers do not understand the concept of mixing latency. It's EXTREMELY rare that somebody does a thorough review of a sound interface. In fact, I think very few people in general understand how big of a difference a good driver has on overall CPU load + low latency performance.

It used to be a big topic about a decade ago, when ASIO drivers were first introduced but for some reason it isn't any more. It was also one of the major benefits of all DSP plugin platforms like UAD/PT hardware.

Computers have gotten so powerful that even if you only get "usable range" from about 50% of your CPU usage it means you can probably run hundreds of plugins.

The real issues start appearing with all the latest thorough emulations of analogue hardware that naturally require quite a bit more CPU cycles, so it's very possible to run into latency related crackling at quite a low plugin count.

The annoying part here is that once you've worked with a system that doesn't require you to disable a bunch of plugins and runs flawlessly on 64 sample buffers, it's very hard to go back to "normal".