Hmmm maybe if you're talking about developing from scratch, but most developers have a lot of knowledge and assumptions about existing implementations of infrastructure; also, in many organizations developers don't have to think too much about implementing the infrastructure, someone else takes care of that. And at the very least, there's a separation of concerns: you don't have to think about both at the same time.

Actually, re-reading your comment, I'm not sure what you were trying to say. I may be agreeing with you.

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I think it is possible for serverless to supplant PaaS et al, but I don't know if it's quite mature enough yet.