Nor does off-wiki collaboration require that a formal entity be in existence. Off-wiki activities -- whether social meetups or more formal outreach efforts to GLAM institutions and elsewhere -- are no less effective for being organized by loose groups of interested participants. So long
as
there is no need to handle substantial funds -- and how much of
Wikimedia
contributors' typical work requires such? -- the lack of a legally constituted organization matters little.
But to take this one step further, let us assume -- for the sake of argument -- that the activities of the contributor community _do_ require the existence of a dedicated legal entity in a particular jurisdiction. One could, potentially, construct a scenario where this is the case; for example, someone wishes to donate a set of copyrighted works, and
prefers
that an organization subject to local laws be responsible for handling
the
process. Even in this case, however, there is no requirement that the legal entity be a "chapter" of the Wikimedia Foundation -- or, to be more precise, that the entity have in place a particular sort of trademark usage agreement with the WMF. I can think of no conceivable need that could be filled
by a
local entity holding rights to (non-commercial!) use of Wikimedia trademarks but could not be filled just as well by a local entity identical in
every
way save for the lack of such access to said trademarks.
And just to add to the argument, the projects are divided by language, and not by jurisdiction. Whereas in many cases it may be unimportant (for instance, we can safely assume that most of the activbities of the Swedish chapter are more related to Swedish-language projects, and if there is any chapter which "caters" to Swedisg-language projects it is the Swedish chapter), this is not correct for most of the major languages (English, French, German, Spanish, Portuguese, Dutch, Russian ...)
Cheers Yaroslav