Because in the last years all the markets have become extremely competitive, including the niche ones. Even if you find an "easy" market and make a product with

Because in the last years all the markets have become extremely competitive, including the niche ones. Even if you find an "easy" market and make a product with weak UX for it – it's only a matter of time before a competitor redesigns your idea into something better (example: HipChat and Slack).