It's obviously not a security benefit, it's just nice to have a little branding so you have some idea what the link you're clicking is pretending to be
As you said, it's effectively the same thing, so why not do the tiniest amount of effort and generate some slightly indicative address?
Because it doesn't help at all. The first four letters of an onion URL are unimportant because they can be chosen with little effort, as you describe.
Following random links and following random links that start with "zlib" is the same thing.