You know how Python is described as "batteries included" because it has a lot of things in its standard library that in most other languages would require downloading and installing third party libraries?
Mathematica is "nuclear power plant" included. It includes not only a very wide range of functions but also a huge amount of data.
For example several years ago they started adding data on biological organisms. They now have data on over a million species of animals, with hundreds of properties for most of them. You could for example with one simple command get a scatter plot showing bird weight vs bird lifespan. Or for mammals lifespan vs number of teeth. It's just a ridiculous amount of data and it is all easily accessible for computing and graphing.
Same for astronomy. It has a ton of data about the solar system. It's got physical properties of numerous bodies, and orbital data too, and it has functions for various astronomical computations. So if you wanted to see how the distance between Mars and Earth varies over time it is a simply command to get a plot of that over say the last 50 years.
Want a list of all geological formations where T. rex have been found? It can make that list for you, because it has a bunch of geological formation data and it has a bunch of dinosaur data.
They've got data on countries, and cities, and geography, and demographics, and economics, and more.
Other systems can beat Mathematica in specific areas, but nothing else comes near its breadth, and in those specific areas where something else beats it it is still usually decent in those areas.