Why did you choose math over physics or vice versa?

[Wastrophysicist]

As I said, math was invented for accounting. Fortunately you can study math without that too. :D

-Dave K

Indeed hahah. But remember Physics is an excellent source of inspiration for Mathematics. You can study Mathematics without Physics, of course, but the study of Physics lead to branches such as Calculus, many contributions in Topology, etc...

Quoting Pierre Bergé, Des rythmes au chaos: " For some results or discoveries, it is difficult to say to which area they belong: to the Mathematics or to physics." If a mathematician finds a result that could belong to Physics, but has no prior knowledge on it, well, he/she may mix both areas, and some Physics may be required.

For studying Mathematics you don't need Physics at all, but for every Mathematician, I'll encourage to have the very basics of Physics while doing research. You don't know what you can find...