I'm not advocating the purchase of bitcoins, simply providing an answer. I have no opinion on whether or not bitcoins are a good "investment."
The transactional friction is a reason the market is small. If it's easier to transact and more people can do it, the supply/demand curves will push the price up in the future. Assuming demand is proportional to the size of the market.
The barrier to entry is a good thing, kind of a safeguard for new users. You are storing real money on your computer, you need to be able to keep that safe. I'm sure someone will offer banking services in the future to solve this "problem" and make it work like any online account, which just happens to be denominated in bitcoins.
they are way too cumbersome to buy, why invest in a currency that the average computer user can't figure out how to buy?