Why do most Passive Buzzer Modules for sale online use PNP transistor?
Yes it would make sense for high or on to be the active state. However in the old days the prevalent logic family was TTL and it can sink much more current to ground than it can source from V+ so active low sort of caught on. In modern CMOS devices the N channel (pull down) transistor has better characteristics than the P channel (pull up) which again gives a bias towards outputs that can sink more current than they source.

Why the PNP it is the easiest transistor to use with an active low output