Every president since William Howard Taft, the commander in chief famously known for his particularly rotund figure, has thrown a first pitch at an MLB game. Taft unknowingly founded the tradition in 1910 when he became angered by a meeting he had with Suffragists, during which he said that if women could vote "power might be exercised by the least desirable person."
In an effort to calm himself down from the thought of gender equality, Taft headed to Washington, D.C.’s National Park to watch a baseball game. There, the president unexpectedly threw the first pitch, and the rest is basically history.
Since Taft's improvised gesture, presidents representing both sides of the aisle have made their debuts on the sandlot. Donald Trump, for whatever reason, has yet to engage in the ceremonial practice of throwing the first pitch on Opening Day. Whether it be based on fear that his hair will fall off, an unwillingness to deal with the swarms of anti-Trumpers likely in the crowd, or failing to live up to the "greatest baseball player in New York" title he once gave himself, the president has avoided the tradition.