A sport or discipline is included in the Olympic program if the IOC determines that it is widely practiced around the world, that is, the number of countries that compete in a given sport is the indicator of the sport's prevalence.
The IOC's requirements reflect participation in the Olympic Games as well — more stringent toward men (as they are represented in higher numbers) and Summer sports (as more nations compete in the Summer Olympics).
Sports may not depend primarily on mechanical propulsion, though there were power-boating events in the early days of the Olympics.
And regarding baseball/softball;
The most recent change occurred on July 11, 2005, when the IOC voted to drop baseball and softball from the Olympic program for 2012, a decision that was reaffirmed on February 9, 2006.
Softball and baseball are two of seven sports, including golf, rugby, squash, karate and roller sports, that will be considered at the 2009 Olympic Congress in Copenhagen for two openings on the schedule for the 2016 Summer Olympics.
From our friend Wikipedia;
And regarding baseball/softball;