There are 2 scenarios where 0? resistors are commonly used:
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Jumpers and links in through-hole boards. They can be placed automatically by machines designed to handle resistors, so you don't need one specially set up to handle wires.
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"optional" resistor settings in surface mount (and through hole, I guess) boards. For instance, I sell LED boards - 8 LEDs on a PCB with current limiting resistors. By default they are set up for 5V usage. Sometimes someone wants one for 3.3V usage, so I reduce the resistor. Sometimes someone wants them for a constant-current source, so they want no resistor. In that scenario I use a 0? resistor. The same may apply for any board where the exact arrangement of components may vary depending on a customer's needs.