VLAN Translation - Service Provider

Hi there, I am trying to understand the benefit or purpose of translating the VLAN in a service provider. We are currently migrating a lot of E-Lines/ELANs and just wondering what's the benefit of doing a translation. One example below.

Node_A:

interface GigabitEthernet0/0/0/1.118 l2transport

encapsulation dot1q 118

rewrite ingress tag translate 1-to-1 dot1q 243 symmetric

​

Node_B

interface GigabitEthernet0/0/0/5.157 l2transport

encapsulation dot1q 157

rewrite ingress tag translate 1-to-1 dot1q 243 symmetric