Reference:
https://docs.microsoft.com/en-us/azure/virtual-network/virtual-network-public-ip-address This is because "Load balancer and the public IP address SKU must match when you use them with public IP addresses" https://docs.microsoft.com/en-us/azure/load-balancer/skus Standard SKU Load Balancer routes traffic within and across regions, and to Availability Zones for high resiliency.