This one is easy: if your customers are very hard to reach, to deliver, to address, and it takes a lot of effort to sell your thing; usually it wouldn't be worth it
Addressability answers a very important question: How easy are your customers to reach
High addressability markets will make marketing so easy for you. However, you will meet a lot of competition
There are open chances in low addressability markets that need some special products with unusual conditions (urgent, sensitive, private, embarrassing, far, rare, nothing gather them, illegal :) … etc.). These markets are very profitable if you know how to reach them (find their gatherings, create a way to gather them, reach them individually … etc.)
The Internet made it very easy to address both low and high addressability markets. Make use of that!