thing-at-point-file-name-chars and whitespace e.g. char 32

[S+*n_Pe*rm*n]

Why doesn't `thing-at-point-file-name-chars; accept " " as an
allowable character by default?
This seems problematic on systems that allow whitespace in paths (not just w32)
;;;
(defvar thing-at-point-file-name-chars "-~/[:alnum:]_.${}#%,:"
  "Characters allowable in filenames.")

;;;
c:/Documents and Settings/All Users/Documents/{...non-whitespace-path...}/
^point     ^(char-after) => 32
(insert (thing-at-point 'filename))
=> c:/Documents

;;;
c:/Documents_and_Settings/All_Users/Documents/{...non-whitespace-path...}/
^point
(insert (thing-at-point 'filename))
=>c:/Documents_and_Settings/All_Users/Documents/{...non-whitespace-path...}/


s_P