For example, large banks need to securely, reliably, and very efficiently process an unfathomable amount of transactions[1]. In this case, kubernetes would be a giant waste of resources and complexity. The former one hampers throughput, the latter one means security and reliability suffer.

For people not familiar with it (me included, actually), it can be mind-boggling what throughput is achieved, and what mechanisms for reliability are in place. Not just in software, in actual hardware; this goes way beyond ECC memory.

[1] Transactions in the bank sense, not in the computer sense, because I don't want to confuse matters more. In the mainframe world for example, there is a difference between "batch processing" and "online transaction processing", but both could be applied to bank transactions. Note that I'm not advocating for the mainframe world here.