This is one of these questions. When it comes to wikipedia many people immediately think about long articles about each topic. Considering the multitude of encyclopaedias you can find in a book shop one thing is obvious: entries can range from one sentence to full pages.
Now people often complain that the encyclopaedias of regional language's wikipedias do have many stubs and just some long articles - well: I would compare these to the kind of encyclopaedias that give you basic information on many topics in just one or two volumes. I would not compare them to the big ones like Britannica, Brockhaus etc.
Of course over time you will find single articles that get longer, others will remain short for a long time, but ... well ... does it really matter? I'd say no - because Wikipedia is not in concurrence with anyone to my opinion - people put us into a concurrence position, but we are not, because the way each language version is built and works is so unique.
Fact is: one can only write about what he/she knows or translate ... well being a professional translator I really avoid to translate also in my free-time if I don't have to. Not having much time to contribute I normally care about the almanac + some stubs related to the almanac ... much more is not possible (see the main page of the Neapolitan wikipdia for the historical events I normally work on). Another thing I of course care about is notions on the city I live in and that in various languages.
Everyone of us editors have something particular they care about ... and I believe that is great - and it is exactly what wikipedia is about: collecting the knowledge of everybody and put it into one huge encyclopaedia.