Help understanding when to use resistors

No. (EDIT: this may not be true since it is open drain - read the next post.)

Usually you don't need resistors between digital circuits using the same supply voltage.

Every rule has exceptions. A resistor may be useful to reduce noise caused by an output switching (slew rate limiting) or as a protection against errors (i.e. drive contention - when more then one device tries to drive the line to different voltage).