Oh they do, but I don’t know what the real reason it stays that way. The only things I could come up with is that they simply don’t care, backwards compatibility (that one doesn’t really make sense to me), or finally that they can’t come up with a better version due to the mathematically good ones already exist in Unix and Linux systems under the GPL.
I’ll be honest, I can’t see that last reason stopping them, but who knows.
It’s a bit old now, but the point still stands. I’m sure the schedulers across all systems have improved since, but it’s a fact the Unix/Linux systems are still better and more efficient.