Not pictured: the cost of switching to DynamoDB when this service inevitably gets shut down in two years.
Spanner is used for a lot of internal Google services, too. Spanner has basically been eating all the other databases Google uses internally. Nom nom nom, every database that used to be something else is now Spanner.
I think the "google shuts things down" trope is justified and something that I wince at every time I see something like this, but GCP isn't a random pet project that loses money and has no users. It's a very successful enterprise business.
(disclaimer: I work at google in cloud, so obviously I have personal bias, but this is just my opinion based on the pure numbers.)