In which scenario you need to create multiple Azure Virtual Networks and Subnets?

Question

if someone can give me a industry example on why do we need multiple Virtual Networks and Subnets?

Answer 1

One vnet cannot span subscriptions or regions. So everytime you need services deployed in to vnets in different subscriptions or in different regions you would need multiple vnets. Multiple subnets are often used to separate workloads for security reasons. Making sure services on different subnets cannot communicate with eachother or only communicate over controlled ports.