It was a unilateral Apple decision. Other platforms were forced to follow them over the next few years to avoid situations like kids texting each other "Can't want for our class trip to the water park tomorrow <insert squirt gun or real gun depending on font>"

Apple made that change around the same time as the Rio Olympics. In the leadup to the Olympics, there was a push to create an emoji for every event. Unicode 9 added emojis for handball, wrestling, water polo, fencing, etc.

However the almost comprehensive set still had some gaps, because Apple veto'd the marksmanship/air rifle and pentathlon emojis... but not in time to prevent the creation of the corresponding unicode glyphs