Why would you put multiple resistors in line vs one resistor of the same value?
Three reasons I can think of:


to allow for a higher power dissipation than one resistor can handle.
to tolerate a higher voltage than one resistor can safely handle.


(Higher power or higher voltage resistors would be larger, which may not be convenient for the auto-place machine)


to minimize the number of different resistor values required on the board (if I use lots of 1K resistors elsewhere, it may be cheaper to use three here, than to buy a few 3K resistors to use in one place)("cheaper" may include loading and programming the auto-place machine as well as the actual cost of the resistors).