First of all, as the sibling comment mentioned, no one is waiting for weeks for hardware requisition. Everyone is using virtualized environments and have capacity to spare. Spinning up a new instance in VMware is not harder (in fact easier) than in AWS and hardware costs are SO much cheaper than Amazon's margins.

Furthermore, If you have spiking workloads or hyper growth and can't do proper capacity planning - that's exactly the original AWS value prop, run a hybrid private/cloud environment and extend to the cloud when needed.