I have been extremely busy with contributions to BuddyPress core, and continue to be busy with client work, so I’ve had to prioritise my time. I have added some fixes and enhancements to Achievements this week, and I have targeted to have a small update out this coming weekend.
I do really appreciate all the questions and feedback, and I am trying my hardest to attend to them all. Again, this is something I hope to be in a better position with at this weekend.
Regarding this particular topic. Points play an important part of Achievements, but they have a limited scope. They are intended as a simple numerical measure allowing both the site admin and other users to compare themselves to each other. For example, Achievements has a bundled high-score table widget, like you might find in a video game. This concept perhaps isn’t best explored in the current version, but this first version isn’t meant to be / can’t be perfect. 
From the wp.org site for CubePoints, “CubePoints is a point management system designed for WordPress blogs.” Looking at the images on the CubePoints homepage, it has features which Achievements doesn’t have, such as “gifting points” to each other, and I believe someone’s even written a virtual store for it. I found a Paypal “top up” addon, too, which seems to allow users to convert real-life currency into virtual points.
Because of CubePoints’ focus on points as well as display of a rank for users, I think this puts it in a middle position between being an implementation of a reputation system, and a virtual currency. If you allow users to buy virtual items (either graphical badges or tokens, or in redemption for physical objects), people who want those items will try to hoard as many points as possible, just as in real life — you want to get paid more money to buy better things, right?
I appreciate this is only one specific use of CubePoints, but if you use points as a virtual currency as well as a reputation system, use of the currency devalues the worth of those points as for reputation.
An area that Achievements and CubePoints have in common is that they are also about increasing community participation and “stickiness” in your brand or product. One more comment might just give them that next badge they’ve been working towards, right? Air miles and store loyalty/reward cards have the same concept behind them, and they are all implementations of social gaming (not in the Nintendo Wii sense!).