Most are (less extreme, that is), it’s just that the more extreme examples make it more obvious what the differences are 
A slight cow hock/turned out (these are often used interchangeably, though depending on who you talk to they are either separate things or the same thing)
But this is the problem - they are not the same things.
You can get more turned out hind legs before you start running into soundness issues, than you can cow hocks. I’d take more extreme turn out, over milder cow hocks, any day, all else equal.
Structurally, they are different, which is why they need to be viewed differently. I do realize that a LOT of people would say the draft picture is cow hocks, but it’s not. If the cannons are vertical, no matter where the toes point, it’s not cow hocked.
does not affect performance, so while it may not be traditionally correct, it is functionally correct and should not be a reason to pass over a horse.
Cow hocks of any degree, and a too large of a turn out of the hind legs, are faults. Always. Neither are functionally correct. The worse the cow hocks, and the more work you’re asking the horse to do, the more likely he is to run into soundness issues, and earlier rather than later.
There’s a reason there are conformation standards for breeds which have breed approvals. They are based largely on what is known about what makes the horse most likely to be sounder, for longer, doing athletic work. That doesn’t mean horses can’t still do high level work, for years, and stay sound (as much as a high level athlete can), but they are the outliers, not the norms. Outliers should never be used to justify treating their faults as normal or ok, let alone desirable.
That’s not the same as saying either one is an automatic dismissal of a horse for athletic use. I’d take a mildly cow-hocked sound 15yo over a very obvious turned out 5yo any day.
