Really it'd just be for consistency with most other code (being able to use a while loop to loop through found files without a ridiculous speed decrease.)

alias listfiles {
  var %count = $findfile($mircdir,*.mrc,0), %i = 1
  while ($findfilecache(%i)) {
    echo -a $v1
    inc %i
  echo -a * %count files found.

Most things in mIRC use loops; $hget, $timer, $read, $window, etc. Only a few rare cases use callbacks.