Linked from
The 7 pages that link to Overblowing, each with the reason it gives.
FluteRelated: A flute player shifts the jet to sound higher modes without changing the tube.
Woodwind instrumentRelated: Overblowing selects higher resonances of a woodwind’s air column.
Pan fluteRelated: Stronger airflow can make a tube sound an overtone rather than its fundamental.
NeyRelated: Ney players use stronger, carefully shaped airflow to reach higher registers.