Azure - What is the purpose of a resource group location?

Most templates in Azure ask you to specify a location(which is Azure Data Center Location) for each of the resources in a resource group.

Every resource is located in an Azure data center, but not every Azure data center supports every resource type.

Select any location that supports the resource type. You do not have to create all of the resources in a resource group in the same location;

However, whenever possible, you will want to create resources in the same location to optimize performance.

In particular, you will want to make sure that your database is in the same location as the app accessing it.

The resource group stores metadata about the resources. Therefore, when you specify a location for the resource group, you are specifying where that metadata is stored. For compliance reasons, you may need to ensure that your data is stored in a particular region.

https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-group-overview

Actually it does matter:

Azure Resource Manager overview:

If the resource group's region is temporarily unavailable, you can't update resources in the resource group because the metadata is unavailable. The resources in other regions will still function as expected, but you can't update them.

For more information about building reliable applications, see Designing reliable Azure applications.

So we could imagine a situation where resource group is defined in LocationA, and all resources in that group are located in different region. When resource group region is unavailble then they may be issues when accessing metadata. Without metadata, it may not be able to failover.

When creating a resource group, you need to provide a location for that resource group. You may be wondering, "Why does a resource group need a location? And, if the resources can have different locations than the resource group, why does the resource group location matter at all?" The resource group stores metadata about the resources. Therefore, when you specify a location for the resource group, you are specifying where that metadata is stored. For compliance reasons, you may need to ensure that your data is stored in a particular region.

https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-group-overview