powershell - are validation parameters really useful? -

I'm studying powershell functions and its valid parameters. Although I do not understand that they are really useful.

I make a simple example.

  get-choice function ([parameter (mandatory = $ true)] [string] [ValidateSet ('y', 'n')] $ option {return $ option} get-election K   
 This function gives me this error:  
  get-option: Impressible qualifier l 'armamento soul parametro' preference 'l' armamento "k" Non-aperture al set valid according to "Y, N" Specification Valid Furnir ur Armeno inclusive so many nail sets Ed Egmore de Neuve il Comondo Riga in: 6 cars: 11+ receiving options & lt; & Lt; & Lt; & Lt; K + category Info: Invalid data: (:) (meet), parameter binding validity exception + Fully Qualified Errida: ParameterArchiveErrorization error, get-option   
 If I do not specify a valid group of values So I can see them within my code:  
  function get-choice 2 ([parameter (mandatory = $ true)] [string] $ option) {if ($ option - Y 'and $ option-' n ') {write-host "yes and no you I have to choose between "return", choose option, 2-k   
 and I'll get more friendly message:  First of all I would like to know whether the error It is possible to customize the message I  and   
 so I hope someone can explain why I should first prefer the approach. thank you in advanced.   
 
 
 Some reasons to use standard validation:  
 
 Annotative code ; 4 lines of code compared to 1 line with very little (again  return  statement)  
     > There may be some bugs in the custom code  
 PowerShell's VS may contain some custom verification messages (?) (Just dreaming)  
 ...   
 Check - Post @ Geek You will see how you can customize the error message. It's a little developer oriented, but it's worth reading.