Do you have some magical way to get files from the internet to your vita that doesn't require using the internet that you'd like to share?
In regards to why, it's an all-on-vita way of installing homebrew that doesn't require a PC, that is more than enough reason
Rather obviously you're taking that to an extreme out of context. No one said anything about not needing the internet, shocking as it may be to you we're not all retarded.
The point was and let's bear in mind I'm just talking about my own use case, not the entire world, that you are still just using the Vitas WiFi connection. Not that that's much of an issue for small files, but where that file originates, be it local or remote the process is much the same.
I just don't consider it a hardship to transfer a file from my computer. Which is generally where I keep a backup of everything because I'm a bit of a hoarder for some things. So in your scenario I'd have to download it to my Vita, install it, then transfer it to my computer if it was something I'd like to keep a backup of. I'm not seeing an advantage there.
But yes it's convenient in some cases, if you're out and about away from home you can just download whatever from the website directly. But then I can access my files remotely too so again, for me meh, not much difference.
However we don't all do that sort of thing, which is why other options exist I guess. I'm not one to assume that everyone must have the same opinion, needs, wants and likes as I do. Which is why I suppose I tend to put forward rational explanations rather than ridiculously extreme and out of context statements.