I doubt this shop ever did a ton of business, but there's a lot to be said for the practical value of having a small shop selling various sundries in such a remote part of the park.
The main building at Rafiki's Planet Watch is 20-30 minutes away from the shops in Africa, by the time you consider the long walk to the train station, waiting for a train, riding the train, and the short walk on the other end. In essence, it should be viewed as a mini park of its own, with all the facilities associated with that. Just there needs restrooms out there, it's not unreasonable to expect there's a place where guests can buy sunscreen, packaged snacks, pain killers, small toys, (undoubtedly film and batteries in an earlier era), etc. without having to make the long trek back to the "mainland."
I'm not sure if they're currently open (Covid-convenient budget cuts, and all), but the small gift shops at TTC, outside Epcot's gate near the bus stops, and the gazebo in front of DAK are great examples of similarly unglamorous-but-necessary stores that carry basic supplies to help people start and finish their day as they enter/leave the respective parks. They are part of a longstanding tradition dating back to the 50's, following in the footsteps of the Newsstand at Disneyland (most similar to the small counter kiosk in DHS that can be accessed from either side of the turnstiles), providing basic necessities and small souvenirs for guests who find themselves unexpectedly needing something.
Disney's parks are a premium product, and it's perfectly reasonable to expect that there are some locations in the parks that aren't as profitable as others, in order to maintain a level of convenience for the guests. Just like you can find food locations open well outside of normal mealtimes, basic necessities should be reasonably accessible from anywhere in the park.
I doubt many people ever purchased their favorite souvenir at this location, but it provided a valuable addition to the park's overall roster of offerings. Similar to how smaller exhibits and walk-throughs can help round out a park's attraction roster, there's a lot to be said for the value of small out-of-the-way locations like this and the convenience they offer.