I think the idea is that they could store the data in BigQuery, and point users of the site there.
Sure, but now you're moving the site from "Free data presented in a pleasant way to view" to a "pay-as-you-go database". Your audience shifts dramatically, and you lose the ability to share the data you're trying to present.
There is also the deep magic...
https://github.com/phiresky/sql.js-httpvfs
The crawlers would have still just hammered their site though, right?
Sure, but now you're moving the site from "Free data presented in a pleasant way to view" to a "pay-as-you-go database". Your audience shifts dramatically, and you lose the ability to share the data you're trying to present.