What I personally want from namespaces on crates.io is basically the same as I want from org names on GitHub; the ability to manage permissions at the level of a organistation rather than each package requiring a unique setup, making it harder to audit and admin all the packages belonging to an org. It also seems like a win for consumers to know when they're using code from a specific vendor vs when they aren't. The consumer trust problem you can possibly solve with naming conventions — although it's hard to ensure that everyone has the same conventions unless it's enforced — but the admin problems you can't.
Yes, it would be great to have packages grouped by organisation. It would make it much easier to see in a package list how which organisations you're depending on, rather than just how many crates.