I think that's partly because the idea of using your phone as an actual music player also happened to take off around the same time.
I remember when phones had the smaller version, but it was used primarily for headsets.
I remember when phones had the smaller version, but it was used primarily for headsets.
A little while later, someone released an adapter, and that lessened the annoyance.
But later phones that had 3.5mm (or 2.5mm) in-built were definitely better.