Because Wikidata is an incredibly complicated project, one that even many Wikipedians don't really fully understand the nuances of -- good luck explaining it in a sentence or two on a small mobile screen :) More generally, though, Wikipedia is our flagship project and the only one with broad name-brand recognition. Wikidata has many important applications, but the foremost is to provide structured data for and about Wikipedia -- so, while vague, "help[ing] Wikipedia" is in fact what you're doing by playing these games. Yes, we'll test a secondary screen that has a bit more explanation of how this tagging helps Wikipedia (e.g., test a few bullet points like "it will make Wikipedia information easier to use in other languages," or "it will add more context when you search," etc.). But I do want to balance instruction with ease of use; the whole point of this kind of contribution is that, unlike freeform editing, you shouldn't need to read a manual to feel comfortable doing it. All the copy in these prototypes is still very much TBD, and we definitely haven't nailed down the UX for a live-in-production MVP. Our challenge for the rest of the quarter, through a combination of in-person testing and alpha/beta user validation, will be to find a framing that works in both tone and substance -- something that won't scare people away ("ack, it's a quiz!" or "ick, it's an ad!") and will provide them with a value proposition that makes sense -- because for a feature like this, the devil is really in the details.