Warum kein !-Zeichen möglich?

@echo off &setlocal

<nul set /p "=Enter your password: "  
call :HInput pw
echo Input length is %errorlevel%
setlocal EnableDelayedExpansion
echo Your password is %pw%
pause
goto :eof


:HInput [ByRef_VarName]
:: inspired by Carlos @ www.DosTips.com
if "%__HI__%" neq "__HI__" (  
  setlocal DisableDelayedExpansion
  set "S=" &set "N=0" &set "__HI__=__HI__"  
  for /f %%i in ('"prompt;$h&for %%i in (1) do rem"') do set "BS=%%i"  
)
set "C="  
for /f "delims=" %%i in ('2^>nul xcopy /lw "%~f0" "%~f0"') do if not defined C set "C=%%i"  
set "C=%C:~-1%"  
setlocal EnableDelayedExpansion
if not defined C (
  echo(
  if "%~1"=="" (  
    echo(!S!
    endlocal &endlocal &exit /b %N%
  ) else (
    if defined S (
      for /f delims^=^ eol^= %%i in ("!S!") do endlocal &endlocal &set "%~1=%%i" &exit /b %N%  
    ) else endlocal &endlocal &set "%~1=" &exit /b 0  
  )
)
if "!BS!"=="!C!" (  
  set "C="  
  if defined S set /a "N -= 1" &set "S=!S:~,-1!" &<nul set /p "=%BS% %BS%"  
) else set /a "N += 1" &<nul set /p "=*"  
if not defined S (
  endlocal &set "N=%N%" &set "S=%C%"  
) else for /f delims^=^ eol^= %%i in ("!S!") do endlocal &set "N=%N%" &set "S=%%i%C%"  
goto HInput