Note that bitcoin is not anonymous by design. There is a certain level of privacy, but all the transactions are publicly logged.
Bitcoins are aimed at everyone. To find out the motivation of the current userbase you would have to survey all users

But yes, currently there are mostly tech geeks, libertarians and some drugs fans (money laundry isn't very popular in my opinion).
I think bitcoins would simplify online payments and transactions. For example, I live in europe, but I like dealextreme.com because they offer free shipping and they have cheap stuff. It would be cool if they let me pay with bitcoins and avoid the fees from Eur/USD conversion. Other area where bitcoins could be useful is micro-payments.
Your mom probably won't use bitcoins anytime soon (or ever). If bitcoins take off, they will take their place as an alternative way to pay online. So if bitcoin succeeds and if your mom shops online, she might use bitcoins in a few years.
I hear what you're saying..
I, personally, feel the level of 'technical' knowledge is a little too advanced for the 'mainstream' crowd. Think of the folks that don't even understand or know how to use torrents. If this is the ultimate goal for BitCoin, it needs to really simplify the process.
It seems to me that BitCoin is sort of like an "underground currency". I'm not knocking it. It's the lack of mainstream that draws me to it.
I do appreciate your post though, it help provide some insights.