You can, but...

Some do actually use supercomputers to do mathematics.

Most however, thrive in an actual academic environment including spending a lot of time interacting with other mathematicians and going to conferences. There's a big difference between living in an academic environment and spending your whole life thinking about math and being around people who do the same... and working a 9-5 and doing a little math on the side. Not to say it isn't possible, but most reasonable jobs don't leave much left over mental energy for doing maths.