Copyright, when wikimapia started they did not consider how their geodata was copied. It is now heavily encumbered by copyright and unusable out side of the site. Things may have changed; it has been almost twenty years since Wikimapia started.

But yes I loved wikimapias concept, but using the data ment that everyone who cared about that used Openstreetmap instead. And since the goals of OSM and Wikimapia differ a bit you wont have that discussion you are talking about.