There’s a famous quote that goes something like “why do people rob banks … because thats where the money is”. When people are considering new niches to go into the often forget that common logic. Unless there is some sort of demand building the best website in the world in that space will yield very limited profits. Another aspect that’s often forgotten is the need for instant gratification.
Do you think there are more people who want to eat healthy foods in moderation and exercise on a regular basis, lose weight slowly and safely, or more people who want to take a magic pill and be thin in 30 days? Do you think there are more people who want to work hard for 20 years scrimping and saving on the way and have a sizable nest egg for retirement, or more people who want to get rich quickly while lounging at home in their underwear? While the examples above are extreme they are really just to make a point, it’s easier to sell someone something they want even if they know it’s not something need, or is good for them. So build sites that cater to these wants and desires, desperate people are more likely to search wider and click deeper into the SERPs.