Let's say you enter the "weight loss" niche, which is actually a market, but let's assume for now it's just a niche.
You write an article which brings in lots of people/ have great SEO results or whatever your traffic source may be.
You set up a website with lots of useful information about weight loss.
But once they land on your page, why should they stay? why should they opt in? They've seen at least tens of these websites before (if not hundreds or even thousands!).
So my point is: every website should have an USP, right? after all, why opt in in your list when there are so many other available? especially when you just start out (later it might be easier b/c you already have some reputation).
How are those who apply this viewpoint doing and how are those who don't?
Is your website just another brick in the wall or do you offer your solution using a different point of view (notice I didn't say offer a different solution)?
Do you research and see how others are doing it so you can be different before you start a new website?