To be honest, as someone who is usually quite uninterested in writing plot summaries, I kinda want to flip the question that started this conversation: do we… need detailed plot summaries? If people want to know every little thing that happens in a story, in the order they're presented on in the story, surely they just ought to go read/listen/watch/smell that story. The Wiki's strength rather lies in spreading all that information to the in-universe pages. A lot of Wikis do just fine without detailed plot summaries and just have more-or-less-detailed synopses.
'course, this is all idle musing. The reason we're going to keep having plot summaries is the same reason we're going to keep having pages about grapes and bicycles and what-have-you: we've put a lot of work into having them already, there are consequently a lot of them around, they don't do any harm by being there… so all in all it'd be silly to stop now.