[RyanN]

It's much easier to manage and organize. If you have a robot.py file that is 10k lines long, how much time is it going to take to find where you initialized the joysticks?

If you have it under /robot/joysticks/joystick_left.py, you know exactly where it is, and is likely 20 or 30 lines long in total.

Also, imagine you have more than one programmer, you can give each programmer a subsystem to work with. The changes they make are isolated to their subsystem and don't affect the code of other people's code / subsystems.

Code management is a primary reason.