many reasons, but there are a lot of great tools for data visualization. If you ask me why Tableau is better than the others, my answer would be, the Community.
When I started using Tableau, the Tableau Community Forums helped me a lot. No questions are left unanswered, and you'll find a lot of people that are eager to help you. Don't hesitate to ask any questions here: https://community.tableau.com/community/forums.
The community is all about sharing. There are many events where the Tableau Community gathers to share. The Tableau User Group (TUG) is a regional event (check whether there's one near your area!) where senior users meet new users and discuss new features, tips, use cases, and more. It's also a great place to share pizzas and beers!
Don't be sad if there is no TUG near you; there are many online events, such as the Fringe Festival, that are organized by the Tableau community: http://www.thefringefestival...