What would they be plugging these USB flash drives into? Underdeveloped countries / regions have very low penetration with traditional laptops / desktop computers. But nearly everyone has a smartphone of some kind, which has WiFi. That's the reason the form factor of these are mobile hotspots.
Isn't the idea that you only need a minimal device with a browser to access stuff on the portable hotspot? Handing out USB drives would be easy, but people who had only phones might not find them as practical (and they'd tend to get wiped / sold / lost / etc.)
At the least you need storage for the content ($10-20), and a physical device to read it off of ($20-40). If your community has lots of computers with no wireless antennas (old servers), USB keys that can be passed around make sense. If you have lots of mobile devices with wireless (phones or tablets), a hotspot like this makes sense and can be used by dozens of people at once.
In practice USB keys run a slightly higher risk of being wiped and repurposed for personal storage. Some IIAB users glue the SD card into their socket for that reason, making it take a lot longer to swap out.
