[pclmulqdq]

Unless you build your network for it, multicast is a huge pain in the ass to administer. None of the big cloud providers built for it at the scale that traders use it, and I think they prefer things that way. When customers want it, they all just fake it by doing fan-out unicast.

[rcarmo]

All hyperscalers have an SDN that essentially spoofs local ARP/DHCP inside the hypervisor and does not support broadcast or multicast by design (there are some caveats here, since some telco protocols that require them can be made to work).