I see nothing exceptional about this, and "using the MBA like a computer"? Well we had bought an iPad and neither of us like it -- we both like having a real keyboard, separate user accounts, a browser that will work on Flash sites, ability to have more than one application viewable at the same time, all in a package about the same size as the iPad. ... I'd certainly say the MBA is being used "like a computer" (whatever that means) as are the other Macs we have. This one just isn't being used as a heavy-lifting computer. And neither is the one of the OP's mother.
Because he's not using more than 64GB of storage space?
Can I remind you that nuclear bombs, space shuttles, etc. were all designed with computers in an era when a *megabyte* of memory was almost inconceivable?
So you're using your computer more like a "computer" than the people who invented, say, the techniques to sequence the human genome, because you downloaded some crappy movies from iTunes and they're clogging up your drive space?
I have a 64GB SSD with nearly 33GB of free space left. That includes all my music, photos, documents, etc. Some people don't have a lot of stuff on their computers.