The former come about because people take video directly from their iPhones or Android devices, do some very basic editing with whatever tools are available, and post it online. Video on Instagram comes in two forms: low quality hand-cam videos and well-produced content. What’s much more difficult is uploading video. It’s easy to take photos with a mobile phone, it’s easy to use one of the many image editing apps to tweak them, and it’s easy to upload them. This makes managing an Instagram account for a business quite a difficult task.
Instagram has always been a heavily mobile-focused app, and it was only relatively recently that you were even allowed to access it from a non-mobile device.