It's not that weird, they put the alias' in so new admins on windows fresh from linux don't hit a complete roadblock at the first command they type. Its to make powershell less punishing to learn, not emulate a different system.
So imagine when they packaged that for Mac, that assumption is no longer true.
I would argue that for scripting portability, this should be the same. With wget equivalent in Powershell being so different for example, scripts that use aliases will be broken.
Granted, don't use aliases in scripts and all that.
FWIW, I always thought of it as being for portability of humans, and was very grateful for it on Windows. A large chunk of my time is spent on *NIX systems, so my fingers automatically type "ls" and "rm" instead of "dir" and "del". The fact that Powershell worked, rather than throwing a "eh, what?" error made my time on Windows suprisingly more pleasant.
They should have implemented these with a missing command handler. So if the ls wget etc exist they work. But just before the command line complains of unknown program name it should check that list and execute the alias.
A new "bottom of the stack" alias instead of the current one that takes precedent over executables.
So imagine when they packaged that for Mac, that assumption is no longer true.