All it does is help me find when and where I took a certain photo of a certain species so that I can find it in my many bird photo folders.
You don't have to take or upload any photos if you don't want to, it's just very helpful to have media on eBird, and I'm glad you do upload photos of rare/uncommon birds. For me, photographing birds is enjoyable and I try to upload at least one photo to eBird for each birding trip. When we started birding, our cameras were all we used and we didn't have binoculars for years, so I guess that helped us get good at using cameras. But I understand not wanting to go through the trouble of taking photos and instead using that time to enjoy the birds and outdoors.