Well, I'm not as convinced as to the 'why' in one's own private cloud (though if you're large enough to have a true separation of concerns, and a dedicated team

Well, I'm not as convinced as to the 'why' in one's own private cloud (though if you're large enough to have a true separation of concerns, and a dedicated team to administering your cloud, fair enough), but for a public cloud, the ability to fire off a small snippet of code and pay nearly nothing for it, and do very little to make it production worthy is really beneficial. It allows you to write rules like "every time I do X, execute this bit of code", without having to spin up servers or capacity plan for it; that's left to the cloud provider to do. It also allows you to build 'Serverless' style applications, by even making your incoming client calls just execute FaaS to figure out how to act and respond. Altogether the benefits are the application developer doesn't have to worry about the VM security, scaling, etc. They just write their code, and it scales transparently, on VMs managed by the cloud administrator. For an immediately obvious use case, if you're in a cloud already, you can execute a FaaS as a cron job. Then, you don't have to worry about "where do I execute this" (is it sharing a VM? Does it get its own VM?), with the associated tradeoffs; you just point the cloud's cron scheduler to the function, and you're done.