a lot of the cheap solar garden lights run off of a very cheap rechargeable AA battery. Additionally, they are generally not water-tight. So the battery goes bad/corrodes, and the lights stop working. Six months later they get thrown out.
@sailbyc Walking around a neighborhood, noting the failed lights, and offering to “dispose” of them can get you lots of little panels for cheap (and save them from the landfill) but they will need batteries and cleaning. They often also need a new acrylic cover, as the cheap plastic cover over the solar panel is often not uv-stable, and gets super cloudy when used outdoors.