This is a major reason the cloud commands such a premium. It’s a way to make down time someone else’s problem.
The other factor is eliminating the “one guy who knows X” problem in IT. What happens if that person leaves or you have to let them go? But with managed infrastructure there’s a pool of people who know how to write terraform or click buttons and manage it and those are more interchangeable than someone’s DIY deployment. Worst case the cloud provider might sell you premium support and help. Might be expensive but you’re not down.
Lastly, there’s been an exodus of talent from IT. The problem is that anyone really good can become a coder and make more. So finding IT people at a reasonable cost who know how to really troubleshoot and root cause stuff and engineer good systems is very hard. The good ones command more of a programmer salary which makes the gap with cloud costs much smaller. Might as well just go managed cloud.
I never understood the argument of a senior IT person's salary competing for the cloud expenses. In my contracting and consulting career I have done all of programming, monitoring and DevOps many times; the cost of my contract is amortized over multiple activities.
The way you present it makes sense of course. But I have to wonder whether there really are such clear demarcation lines between responsibilities. At least over the course of my career this was very rarely the case.
Surely 'the other factor' is no factor at all as IaC can target on-prem just as easily as cloud?
Many people do inaccurately equate IaC with “cloud native” or cloud “only”.
It can certainly fit into a particular cloud platform’s offerings. But it’s by no means exclusive to the cloud.
My entire stack can be picked up and redeployed anywhere where I can run Ubuntu or Debian. My “most external” dependencies are domain name registries and an S3-API compatible object store, and even that one is technically optional, if given a few days of lead time.
That is called "bus factor" or "lottery factor". If the one IT guy gets hit by a bus or wins the lottery and quits, what happens? You want a bus factor of two or more - Two people would have to get hit by a bus for the company to have a big problem
There's a bus factor equivalent with the cloud, too. The power to severely disrupt your service (either accidentally, or on purpose) rests with a single org (and often, a single compliance department within that org).
Ironically, this becomes more of a concern the larger the supplier. AWS can live with firing any one of their customers - a smaller outfit probably couldn't.