Well,
that's how the VM is configured. Your picture in the bottom right shows it. 2 sockets (CPUs) with 4 cores each = 8 vCPUs.
Performance wise it shouldn't matter if you configure 2 sockets with 4 cores or 1 socket with 8 cores, as you will always get 8 vCPUs.
In earlier version of vSphere this option wasn't even available.
I think it only matters when your Applikation inside the VM is licensed for sockets. So you can configure your VM according to your license.
Tim