There are MANY reasons why you should consider creating a directory website. It is an excellent value-add, lead generator, and income generator.
You can create them for niche areas versus just a straight Yelp clone or Travelocity clone, which I do not recommend.
If you are a web developer, it would be a great tool to contact businesses then later sell on a development project. Or to give premium listings to your existing clients as part of your care package.
Or you can also create a directory for your local city or town and sell advertisements or advertise your own business.
You can make a directory website with WordPress for churches, associations, etc. The opportunities are limitless.