David Heinemeier Hansson

Clouds and VPS's work on the principle of buying in bulk and selling by the piece. Serverless allows for slicing the server thinly, but it may not be a good deal if you need all the computing cycles. It can also lead to lock-in.

Don't be fooled by serverless

If you need the computing capacity of a single server, having that server is smart.
However, other than cloud providers, shops operate solutions, not servers, so their total cost of ownership for that server also includes their administration.
Maybe doing the whole math still shows an advantage of owning the server, but the true comparison has to encompass the following:
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Development costs. Serverless is all container-based. Basically, one gives a container + config to a container runtime service, such as ECS or Fargate. Running an app on a server means deploying/configuring/patching all app runtimes on the server.
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Continuous integration costs, including all that often-forgotten deployment code required to provision/config servers.
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Operational costs - The OS on the server needs patches, which also has downstream effects on the application runtime layers. All doable, maybe easily, depending on skill set, but not free.
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Operational and maintenance costs of on-premise services are not considered obviously. Also, serverless approach would fit greatly on startups and early stage products where you do not have much traffic then you pay almost nothing during that time.
I am not even talking about scalability and availability of cloud services.

So much of “best practice” cloud infra is just lifted directly out of AWS marketing material. Why do something simple when there’s so much money to be made on you through complexity?

Very true, AWS and other cloud providers are pretty hyped up