There a infinitely more irrational numbers than rational numbers, so if one were to search for a special number like π or e, they are more likely to find them to be irrational than rational. It would be instance coincidence if those numbers would be something nice and even. And since almost everything in math is derived from either π or e and you can't simply divide or multiply away irrationality (except with another irrational number) this irrationality tends to stick around. We essentialy have a π centric number system inside the decimal system, that's why π gets its own symbol. No mathematician ever writes out π as a 3.1415...., so for all that matters the symbol π is nice and even.