A lot. It's the same reason amazon doesn't sell servers and instead gives you access to a single instance that everyone pretends is the same but in reality is massively transient.
We give full bare metal access. If you just want one GPU, we give you a VM with PCIe pass through. If you take a whole box, we can give BMC and can give you access to the PDU itself, to hard reboot things remotely. It is as if you own the whole machine yourself.