It’s unclear to me at this point why people are contributing to Wikipedia and certainly wikidata, but they’re getting something out of it (perhaps notoriety), and a lot probably has to do with contributing to the greater good. It’s all non profit. The rest of the web is unlike these stand out projects.
Meanwhile, why would say Mouser or Airbnb pay someone to markup their docs? WebMD? Clearly nothing has been compelling them to do so thus far, and when you’re talking about harvesting data and using it elsewhere, it’s a difficult argument to make. Google already gets them plenty of traffic without these efforts.
They do it because it benefits them too. OpenStreetMaps links with WD, GLAMs link with WD, journals/ORCIDs link with WD, all sorts of other data archives link with WD. Whoever is not linking with may see a crawler pass by to collect license-free facts.
Also, I just checked: WebMD is using a ton of embedded RDF on each page. They understand SEO well as you said :)
Meanwhile, why would say Mouser or Airbnb pay someone to markup their docs? WebMD? Clearly nothing has been compelling them to do so thus far, and when you’re talking about harvesting data and using it elsewhere, it’s a difficult argument to make. Google already gets them plenty of traffic without these efforts.