It might be because they get tired of their old names.
names on uniforms
Angels, Athletics, and Astros
The Cleveland Indians.
New York Yankees
Yankees, Astros, Expos, Rays
Oakland Athletics
Baseball team names that start with the letter "A"AngelsAstrosAthletics
San Fransisco Giants and the Texas Rangers
Philadelphia Phillies and the Pittsburgh Pirates
The Florida Marlins and the Tampa Bay Rays.
There is more football teams than baseball teams, football has 32 and baseball has 30