It's been a while since I was in a position where I regularly watched servers boot, but 2015ish I was doing a lot of 'boots on the ground' sysadmin and virtuali

It's been a while since I was in a position where I regularly watched servers boot, but 2015ish I was doing a lot of 'boots on the ground' sysadmin and virtualization work. Servers do a lot of additional testing during boot-up, temperature sensors, RAID cache batteries, memory and RAID arrays are all checked. Some of those checks can be disabled, but you don't really reboot production servers regularly so you typically wouldn't want to. The extra 3 minutes of boot time is much easier to deal with than a bad host coming online. On top of all that it's pretty standard (at least in the VMware world) to store the OS on an SD card. So the OS has to be read into memory and ESX is kinda slow to boot even if installed to a disk.