Why GCP's Project ID is designed to be globally unique?

Thank you so much for you video mister. A little question: How globally-unique is a ProjectID, a bucket name, or even a Service account?
is it globally-unique just inside an organization? or is it considered any organization around the world? I ask this because I've created projects IDs with names like "thisisaname" and GCP doesn't give me any problem, It's strange for me that any other user around the world didn't use a project id like that, so it lets me think that they are just globally inside and organization...

Nice. Just the way Cloud Storage bucket has a Global Namespace and it demands globally unique , may be since VPC is a Global resource, does it matter and mandate uniqueness?

Thanks for your videos