It seems like some coaches and teams intentionally do their tryouts earlier than the majority of the teams. If they can pressure players to accept and it works great for them. But they've got to be setting them selves up for some of the stronger girls to wait til most of the tryouts are done before committing.
When DD was coming up through the softball ranks and we were a small independent team we would try to schedule our tryouts before the marquee organizations in order to pickup a few girls who liked our coaching style and team chemistry. We could not compete head-to-head with the big organizations and if we scheduled tryouts after them, we would get nothing but leftovers and players with baggage (psycho softball parents).