They serve some purpose: I think a lot of places with regular meetups don't post them to the site, and I don't know of another good way to find out about them. (Perhaps the wiki page should be linked more prominantly?)
I also think that if we're not going to include meetups that are not new in the meetup roundups, we should be employing another method to call more attention to them for the sake of newer members.
At the very least, the "only new meetups posted" policy should be clearly advertised with each post, lest a newbie think that the advertized meetups are all that are taking place.
Although it would take more effort to implement, the solution I think would be most effective would be to have separate Main, Discussion, and Meetups sections for the site.
I propose for comment the following alteration of the LW meetup promotion policy:
* The weekly meetup roundup will contain, in its title, only the names of cities which have not previously had an LW meetup, or which have not had an LW meetup in the last year.
* On occasions where no such name appears in the title, the meetup roundup post will still appear in Main but will not be Promoted.
* Cities having a first-time meetup, or where a new meetup is being started by a new organizer after a hiatus, should have additional info about that meetup and its organizer appearing in a prominent, top-of-post position in the roundup post.
This is intended to make it easier for new meetups to gain attention, by requiring hopeful LWers awaiting a new meetup in their area to pay attention to a smaller number of promoted posts and a smaller number of cities appearing in the titles of Main posts.