Having a devops team with the necessary expertise in Google Cloud or AWS is still a supporting function. You've just traded one skill (managing physical servers) for another (managing proprietary virtual resources).

Hence we get caching. There's the farms, then the inbound warehouses, then the distribution centers, then the grocer, then our refrigerators by the dozen or dozen and a half. When your local cache is empty of eggs, though, it requires a trip back out to the grocer to get an egg even if you need nothing else that trip. Then you generally have to buy at least half a dozen if not a dozen or more eggs just to get the one you wanted.

If I have my own couple of hens, I can go out into the yard and get an egg. If that's the whole of my fetch list, it's much more efficient for this single egg to have the hens laying right out back.

This whole few baskets metaphor breaks down from another point of view, though, when we consider that by the very nature of using a globally distributed hosted service we're actually eliminating a single basket problem. Yes, there's not much choice among just Google, Amazon, and Microsoft. (That they are the only options is a bit of a strawman, but lets grant this one legs.) However, putting just your own employees in charge of all your infrastructure in just your own datacenter(s) in just PostgreSQL or just MySQL is another single-basket problem. Spreading it out so that someone else gets to manage the hardware and the service and replicating your data widely within that service is from that point of view more baskets. You get more datacenter baskets, more employee baskets, and more software baskets. Using standard SQL means you can move among compliant software later, too, so you're not as tied to those baskets.

Now, back to your coop analogy. What's stopping me from having my application talk to Cloud Spanner and a local database proxy (or a work queue that sits between the app and the DB or whichever) so I can use Google's reliability for transactions and my local cached replicant for query speed when I'm querying older data? Why can't I keep a few eggs around?

Also, why would I be scared of Google or Amazon "having my data"? Why would I put sensitive data into my own database in plaintext and then replicate it among multiple datacenters that way?

Only if the owner of the chicken-coop has everyone else's best interests in mind. Protip: They don't.

The Cloud isn't about efficiency, it's about data control. Getting people's systems and data into Google/AWS/etc helps with data mining, vendor lock-in, etc. Often times that can be efficient, but also it often isn't.