Under most circumstance, this isn't needed unless you have a big ask. Say, you need 1,000 specific cores and GPUs, then this process is the best way to ensure you have them available.
The original poster probably has the ability to spin up other instance types in their region. If there is no compute capacity in the entire region, something went wrong operationally.
I'm not suggesting you should put in a request for every new resource you need, but if you have a specific instance type or a large number needed, it helps. You're not losing the ability to shut them down the next day if you don't need them, you're just telling the Azure team that you expect to spin some up around a certain time. If you're making a significant request of compute capacity, the team has the ability to reserve those instances for your subscriptions so that you're not competing with others for those cores.
The original poster probably has the ability to spin up other instance types in their region. If there is no compute capacity in the entire region, something went wrong operationally.
I'm not suggesting you should put in a request for every new resource you need, but if you have a specific instance type or a large number needed, it helps. You're not losing the ability to shut them down the next day if you don't need them, you're just telling the Azure team that you expect to spin some up around a certain time. If you're making a significant request of compute capacity, the team has the ability to reserve those instances for your subscriptions so that you're not competing with others for those cores.