Because certain features of vSphere, like for instance HA, are limited in terms of how many hosts and how many VMs they can handle.
vSphere is limited to 96 hosts by the way, are you in a situation where you would need more than 96 hosts in the same cluster? If so, why do you not create multiple clusters? What is the use case? I am asking as we barely see any customers even going above 32 hosts, let alone 64 or 96.
