Design for logos and branding doesn't happen in the platonic realm and isn't focus grouped against brand-unaware Martians; such designs are engineered to serve a real role in the real world, in the minds of real people.
When you propose a super simple abstract logo -- a dot, a circle, a slash -- it works or not depending on if the organization in question is already well known or not.
Thus, proposing such a logo to a client is a form of flattery -- you, yes you, are already so well known you, yes you, can get away with simply having a slash for your identifier! -- and that is all there is to it.
Like all things this can be cargo culted, and smaller clients often want to look bigger than they are, so sure a lot of un savvy operations wind up with fashionably vague and functionally inferior designs, but it's always been that way.
Lastly, it also matters that logos appear all over the place today -- print, web, tv, mobiles, tablets, etc -- and simpler, cleaner logos are easier to make work across all physical scales.
This isn't a problem vector assets solves, either; at smaller sizes you need to change proportions around and generally cheat the spacing -- in short, smaller physical representations look better if deformed into charicatures -- and it is hard to get external parties to respect your rules about which variant to use at which sizes.
Much easier to make something that looks reasonable at all sizes and scales and use it consistently.