In the case that there IS an index page that enumerates all entities you are correct. However, many systems don't provide such an index page.
In many cases it's useful for a page to be publicly accessible yet, not indexable.
This is why sites like YouTube have an "unlisted" level of permission, UUID keys are a convenient way to implement that level of access control.
UUID keys are very useful for distributed systems where a local machine wants to generate a unique key locally, and then later upload it to a centralized store. It's especially helpful in third normal form databases where often you'll need to create objects that reference each other via the primary key.
In many cases it's useful for a page to be publicly accessible yet, not indexable.
This is why sites like YouTube have an "unlisted" level of permission, UUID keys are a convenient way to implement that level of access control.
UUID keys are very useful for distributed systems where a local machine wants to generate a unique key locally, and then later upload it to a centralized store. It's especially helpful in third normal form databases where often you'll need to create objects that reference each other via the primary key.