To make interactive usage easier? PowerShell essentially replaces the text-oriented environment provided by coreutils with an integrated object-oriented one.
In hindsight it probably would have been better if they just had a help message with something like "Oh you must be a *nix user, thanks for trying Powershell! You can do something similar with command xyz. Read that command's documentation -here- , and read a guide on the differences between posix and powershell -here-"
To make interactive usage easier? PowerShell essentially replaces the text-oriented environment provided by coreutils with an integrated object-oriented one.