The terminator resistor value is not arbitrary. It's chosen to match the "characteristic impedance" of the CAN bus wiring. If the impedances do not match, some of the high-frequency signal will be reflected at the end of the bus. Reflected signals interfere with signals sent later.
This Stack Exchange question has some good answers.
Of course, the CAN wiring used in an FRC robot isn't exactly standardized, so the value is more of a good idea than a perfect number.