Why do companies spend the premium of Amazon EC2 and Azure Cloud when there are cheaper and probably better performing providers out there. I.e DigitalOcean or Vultr

In our case I'd say it's the same as the benefits of working with a complete Microsoft stack.

You have better support and a much larger community that comes with the backing of the larger companies.. For some corporations it's not always the expense saved on entry but the continuous savings to efficiencies

Usually its not the only resource you have from them, it's basically IaaS - Infrastructure as a Service.

Cheap is relative.

How much does downtime cost?

Or dips in performance?

Or higher latency due to no local datacenter?

Or the time it takes to sell an unknown provider to the boss.