I think the answer comes from the beginning of the vim-addons manpage:

Manage Vim addons installed system-wide, enabling on a per-user basis their installation, removal, ...

--Ken Bloom

Joey: There's an important distinction to make. A system-wide daemon is likely only to be run by one (system) user, and stay active while the system is active. A vim addon is something that every user on the system may or may not choose to run themselves; if the sys admin installs a bunch of Vim addons, they shouldn't all be enabled (i.e. executed every time Vim starts) for all users; each user should choose whether they want to enable it.

— Ben Finney

Joey: sounds like debconf should really be asking the admin what to do.

— martin