There are many benefits adding simulation capability to the MINDSTORMS® experience, but a few of the more compelling reasons are given below: 

Perhaps the most obvious benefit is that by using a simulated robot we can write programs to work with the robot, even if it isn’t physically available. For example, your robotics club might only have a single MINDSTORMS® robot, but the whole team could be working and programming on a digital version of that same competition robot from home.
When it comes to environments, simulation offers a much greater variety of challenges that would ever be physically possible. Although it might be too expensive to test our robot in the near-weightless of space, we could easily simulate it.