Not the person you're replying to, but...
1: Access to the data center requires either an access card plus biometric verification (fingerprint in one DC in my case, retina scan in the other), or an ID-verified appointment. Then, you still need to know where my server is, plus the access code for the rack (or, you need to be an average lockpicker, but beware, there's cameras...).
2: Each data center has dual-provider AC feeds, plus generators, and provides A/B feeds to my rack. I've not had a dual-feed outage in the last 20 years or so.
3: No cloud provider that I'm aware of guarantees server security or does automated patching (for servers, not services). So, keeping your server up-to-date seems equally important for both cloud and non-cloud scenarios?
4: At least two weeks, I guess? I have sufficient VM host capacity to accommodate 30% unplanned growth, but 100% would require new hardware. So: ordering two servers, installing these in two data centers. But if the new project also requires significant bandwidth, getting new Internet connections in might take longer.
Look, I'm definitely not denying that "the cloud" makes it easier to scale fast, but scaling fast is not an overriding concern for most businesses. Cost is, and self-hosting, even with a pretty redundant infrastructure, is still much cheaper than AWS.