Why do you need to understand Buddhism and its beliefs?

Answer 1

Well, it keeps an important philosophy alive that promotes good will and inspires peace

Answer:

There is no need for any -ism or -ity. However having a philosophy which has been reviewed and commented on by several thousand years worth of scholars helps us in our own meditations on big questions like "How should I conduct my life?"

In the case of Buddhism it establishes some basic premises. The chief being that most peoples lives contain sadness or unhappiness and this condition is caused by desire for things we think we need. It then offers a route (the Eightfold Path) to help us escape this sadness by proposing a simple way to avoid the desires that make us sad and lead our lives in a more skillful manner.

One advantage of Buddhism is that it offers a no guilt religions where people are not blamed for being inherently evil (inherent sin), and proposes that people are fully able to improve themselves without divine intervention.

Answer 2

You don't - given enough time and experience you will reach the same conclusions on your own and become enlghtened.
However it does help to have a map to your destinationn and friends encouraging you from the side lines as you strive for enlightenment.