This is by design and not a good way to script. it better you supply the parameter with the command itself.
e.g.
Get-File -Path
To know the list of parameter and what it accepts you can say as below and will be given the syntax along with example and explanation.
Get-Help Get-file -detail
To full fill your requirement you can create a Script (PS1 file) with Read-Host Command let as below...
#########
#reading the input on host and saving it in variable.
$path = Read-host "Enter the Path"
Get-path -path $path
#########
and there you go. Just type this in Notepad and save it as name.ps1. execute it on powershell.
Hope this helps
Thanks.