Sheer competition. For starters, there’s a ton of competition out there. Depending on your industry, there are likely thousands of businesses just like yours competing for space; targeting a narrower niche immediately alleviates you of some of that competition. Take SEO as an example here; there aa re millions of businesses competing for the top spot in search results for general terms like “marketing firm,” but far fewer going after specific phrases like “marketing firms for personal injury lawyers.”
Another benefit of niche marketing is that it is very word-of-mouth-friendly. People in a niche tend to be in frequent contact with others in that niche, which means more opportunities to get the word out about your business. For example, expectant mothers attend prenatal fitness programs, take childbirth education classes, and shop at maternity clothing stores, where they meet many other expecting mothers.
Research individual companies in your desired niche: If possible, it’s always better to become an affiliate directly with a company (if they have an internal affiliate program), as no one else will be dipping into your commission rate. This is the preferred route for most of the prominent affiliate marketers, including Pat Flynn. Unfortunately, it’s also the most work, as you’ll have to do the research yourself to see who offers programs (they’re usually listed in the website footer).
Concentrating all marketing efforts on a small but specific and well defined segment of the population. Niches do not 'exist' but are 'created' by identifying needs, wants, and requirements that are being addressed poorly or not at all by other firms, and developing and delivering goods or services to satisfy them. As a strategy, niche marketing is aimed at being a big fish in a small pond instead of being a small fish in a big pond. Also called micromarketing.