Extremely basic, context-less example; If I want to have my EC2 boot from an image, I build an AMI, then I put that ARN into a config file or similar and off we go. As a once off thing I would also need to configure some other basic stuff like a VPC, security groups, gateways etc but there's not necessarily any ongoing overheads from that. We're looking at a few config files in total without any specialist knowledge being necessary.
If I want my Supermicro/Quanta/Dell to boot from an image in a similar fashion I have to build the image, I have to host the image, I have to make it available on the network, I have to configure DHCP, I have to configure the BMC (and Redfish is probably not implemented quite right, lets be honest here), then I can boot from it.
Once that's done I've also got to maintain; the host, the BMC and it's firmware, credentials for said BMC (securely), other firmware on the system, the entire network (securely) and a bunch of other stuff I probably haven't even considered. All requiring at least one, arguably two additional domains of knowledge on top of what a normal developer would typically have + a significant up front and ongoing time commitment.