They are small because most of them are true arrowheads or arrow points. They were attached to arrowshafts that were shot using a bow. Most points prior to the bow and arrow were dart points which tipped spears that were launched with an atlatl. These dart points are typically (but not always) larger than the later arrow points.
very true
these are true arrow points used for all sizes of game
i never have understood the meaning of 'birdpoint'
i mean no disrespect to 'BirdPointGris either, i think he has a cool name