That's because Newton was a scientist :-) For some mathemeticians, they don't count since they USE math to do things.
Here's a history of calc I found. Newton and Leibniz are mentioned about 2/3 of the way down. Of course, you can probably find someone to disagree with this.
http://www-groups.dcs.st-and.ac.uk/~history/HistTopics/The_rise_of_calculus.html
Very interesting link. It's still debatable between Liebnitz and Newton, but we should be so grateful to both of them for the contribution.
As a tool, mathematics explains the universe.