Why is greetd greeter user in so many groups?

[kiasoc5]

Hooray, greetd has been merged! [1]

However, according to upstream the greeter user only needs to be in
the video and greeter groups. [2]

Whereas the guix definition for the greeter user has many more groups:

(define %greetd-accounts
  (list (user-account
         (name "greeter")
         (group "wheel")
         (supplementary-groups '("users" "tty" "input" "video"
"audio"))
         (system? #t))))

I can understand the need for tty and input, but why does the
greeter user need the wheel and audio?

1. https://issues.guix.gnu.org/49969
2. https://git.sr.ht/~kennylevinsen/greetd/#manually-from-source