The casino industry is the most profitable by far, followed by porn.
The higher the profit, the fiercer the competition.
There may be lots of hosting companies, but they are not looking to make the sort of money you can make in this industry, so they do not invest the time to learn how to compete to the extent that people in the more profitable industries do.
Therefor, even if the numbers of competitors are larger, their marketing skills are not as honed and the industry will be easier to break into.