Why a new distribution?

For AIMS Desktop, the single biggest goal is making it super easy to get up and running fast. In Africa, we face many challenges that aren't immediately obvious for people from first-world countries. Some locations have horrible connectivity, sometimes its purposely disrupted for political reasons (Cameroon disconnected its entire English speaking population regions earlier this year: https://www.voanews.com/a/cameroon-cuts-internet-in-engli...), so having something that can install everything they need off-line and fast and easy is essential.

Academic institutions who don't have huge budgets are also approached by big software companies all the time who want to make a 'donation' if you'll make the students use their software. Sometimes it's hard for the funding teams to understand why we'd want to reject them, and sometimes it takes a lot of patience and explaining why we want to stay with free software and why it's the right choice for the project.

That's maybe a first part of my answer, on to the broader topic of distributions. I wouldn't view AIMS Desktop as quite a 'distro' per se. It aims to use only Debian packages from the official debian archives. It couldn't quite reach that for this release, but it will probably for buster. There are certainly a large amount of distributions who spend a lot of effort duplicating existing work at no benefit to the larger ecosystem, but that's not what AIMS Desktop is, AIMS Desktop is merely a way of getting a Debian system up and running fast with the math and science software that's used in our curriculum, and we share it because we know of a few other institutions that have been using previous versions (that were based on Ubuntu).

An alternative to releasing AIMS Desktop would've been to just provide a Debian 9 iso, some documentation, maybe another disk/download with a set of packages, howtos on it, etc. But when the installation process goes from 25 minutes to a whole day and becomes more cumbersome for students, tutors or remote IT staff, it can serve as fuel for outside sponsors who might want to coerce us into using more proprietary software. As it is now, the average AIMS Desktop user has no problems installing the system and being productive on it within minutes, our user experience feedback so far has also been very positive and we have many dual-boot students who tell us they never boot into Windows anymore.

The list of software on the website is sparse, yes. The site is still in early stages so it's not quite as polished as we'd want it to be. I think the questions here are very valid and we'll add better explanations of AIMS Desktop includes, why it exists in its form, etc. But I don't think it's really fair to just dismiss it as another 'pink pony linux' distribution either :)

Sorry, I missed the last part of your question "wouldn't a PPA be a better idea":

Yes, currently AIMS Desktop has a ppa, and someone could just do a plain debian installation and add that (it's on my todo list to add those instructions on the site), but our ultimate goal is having every package in the proper Debian archives so that we won't need a PPA for the next release.