To quote MarcoSwart (Bureaucrat and interface administrator on Dutch Wiktionary, not just a random user) whose bot did this: "To use the Data: namespace on Commons we'd need a Lua script to query the data. This would needlessly complicate managing it all." (originally: "Om de Data: naamruimte op Commons te gebruiken, moet er vervolgens weer een Lua script komen om de gegevens te raadplegen. Die oplossing zou ook qua beheer in dit geval zaken nodeloos compliceren.")
If there were a simple way to obtain the data using wikimarkup we'd probably be using the Data: namespace. If there were some off-the-shelf module (that we don't need to maintain) that would allow one to say {{#invoke:mydatawhereisit|SELECT preval-nl FROM Leesonderzoek2013 WHERE woord = '{{{1|{{PAGENAME}}}}}'}} in which "Leesonderzoek2013" would refer to Leesonderzoek2013.tab and putting this on wikt:nl:eland would return "98".. we'd most strongly consider that. (I would prefer it over the current solution but I can't speak for the rest of the community) Actually if that were possible the usage of tabular data would likely explode across projects. Because right now, while I've been told on multiple occasions that I'm not stupid, I'm having quite some trouble figuring out how any of this works.