It's not for every use case, but Big Query is often a very stupidly cheap datastore. Query results get cached, and repeats don't incur a charge unless the data has changed.

It's not a datastore to power a crud app, or anything requiring frequent queries, but it's a great place to stash gobs of logs that you may need to query at some point. Or it's great for serverless batch workloads and is often cheaper in both time and money than firing up spark clusters or something similar to do the work.

Quite frankly, it's awesome. But sure, they do use it as a tool for lock-in, and for some cases it would be prohibitively expensive.