If it’s windy out it doesn’t matter what size yarmulka you are wearing! If you are running or playing ball it doesn’t matter what size yarmulka you are wearing!
And, deiyezooger, bobby pins work fine with short hair (unless you have a chasidishe haircut).
bottom line is that bobby pins are just not part of the modern day yeshivish uniform (no need to put down MO guys who want to make sure their’s stays on).