1) it gives your company a stronger bargaining position with the cloud provider.
Granted, my companies tend to have extremely high spend- but being able to shave a dozen or so percent off your bill is enough to hire another 50 engineers in my org.
2) you may end up hitting some kind of unarguable problem.
These could be business driven (my CEO doesn’t like yours!), technical (GCP is not supported by $vendor) or political (you need to make a China version of your product, no GCP in China!)
Everything is trade offs. AWS never worked for us because the technical implementation of their hypervisor was not affined to CPU cores of the machine, meaning you often compete with other VMs on memory bandwidth. — but AWS works in China (kinda). So my solutions support both GCP and AWS as slightly less supported backup.