You mean c-x c-[fs], right? I'm by no mean an emacs expert although I've been using it for 6 years now, and when I read your comment I thought "Wow, c-x c-a is a functionality? How comes I have never used that?", so I tried that in emacs but it's not mapped to anything.
Apart from that, I fully agree with your comment.
(defun align-all-matches (start end regexp)
"Align all matches of the given regular expression."
(interactive "r\nsAlign regexp: ")
(align-regexp start end (concat "\\(\\s-*\\)" regexp) 1 1 t))
(If you call align-regexp interactively without a prefix argument it does something much like this function but only aligning the first ocurrence on each line, and if you call it with the prefix argument it prompts for all parameters of align-regexp.)