Because people love taking pictures and video clips of themselves and this makes it a lot easier to get shots from different angles. It's perfect for the self-obsessed crowd, for social media influencers, travel bloggers, etc. There is already a competitor and I'm sure future products are going to be improved in terms of sensing, autonomous flying and image quality. I'm not saying Snap is going to be market leader, just that such drones are going to sell.

Also autonomous flying has been in the works for other applications for years, now it's simply trickling down to the cheap consumer level where it can get sold to people who've never operated a quadcopter before and a going to buy this as a fun disposable gimmick.