You are absolutely right about the small niches. What the public hears about is a tiny fraction of the successes (and failures) that are actually out there. If you are lucky enough to find a profitable niche then you don't invite competition to take it away from you. There are several examples that I personally know about that have never been shared with the public.

One example is a personal friend of mine. He developed a B2C software product for a particular niche that you wouldn't think was very large or profitable. He doesn't talk about what he does publicly or even read entrepreneur sites like Hacker News. If someone were to show me his app and ask me how long it would take for me to develop it I would say "three weeks: two to code it and one more to make it that ugly". And yet this guy makes a ton of money (much more than a typical software engineer) essentially for just handling the occasional support or billing issue.

Another example was a guy I worked for in college in the early 2000s. He got in early in the business sending out e-mail newsletters for professional organizations. He bought a license of a high-end e-mail program for about $15k, bought about $5k in server hardware and spent about $750/mo. in co-location fees. Then he hired me and another college student to work remotely part-time at $15-$20/hr. to handle the server administration and support. Add all that up and his total costs were about $20k up front and $2500/mo. The only work he would do is go to conferences a couple times a year and do a couple of sales calls a month. He generally kept the details of his financials hidden from me, but I know that at least a couple of his clients were paying over $5000/mo. each. When you consider he had a couple dozen organizations as customers, that is very impressive for something that is almost completely passive with no technical skills required.