Antennas need to be within a specific inductance range depending on the reader.  When making an antenna the meter measures the inductance to make sure the antenna will tune and to calculate the capacitance value needed to tune it.

It is possible to only use the Tuning Indicator to tune an antenna.  If the loop inductance is too high or low then it will only show IN or OUT.  But the process is easier with an inductance meter.