The filters they have make the pics look "trendy" and retro. It takes a few seconds to snap a pic on your phone, add a filter and upload it w/ Instagram. It's not really photo editing software, it's more like a mobile photo-sharing application. The reason they're grainy is bc they're all taken from a mobile device, and edited on that mobile device. Just a quick way to take a pic, add an effect and share it. Hope that clarifies a bit
