Basketball and hockey coaches wear suits. Football coaches sometimes wear suits too, but often wear team-branded jackets. Some wear ill-fitting pleated khakis, some wear sweatshirts, and Tom Landry, the former coach of the Dallas Cowboys, was never seen coaching without his trademark fedora hat.
So why, then, do baseball managers always wear uniforms?
According to John Thorn, the official historian of Major League Baseball, it goes back to the earliest days of the game. Back in those days (circa 1840-1860) the person known as the manager was actually the team's business manager, the guy who kept the books in order and made sure the road trips were planned and on schedule.
Meanwhile, the guy we call the manager today, the one who arranged the roster and decided when to pull a pitcher, was known as the captain. In addition to managing the team on the field, he was usually also on the team as a player.
There were also a few captains who didn't play on the team and stuck to making decisions in the dugout. They usually wore suits.
With the passing of time, it became less common for the captain to play on most teams. They took on strictly "managerial" roles. Instead of suits of old featured throughout America's dugouts though, the non-playing captains hung on to the tradition of wearing player's uniforms.
President Harry S. Truman shaking hands with Washington Senators manager Ossie Bluege and New York Yankees manager Bucky Harris on opening day 1947.
By the early to mid-twentieth century, wearing a uniform was the norm for managers, with a few exceptions. Connie Mack, who managed the Philadelphia Athletics for a record 50 seasons (1901-1950), was never was seen managing a game without his trademark dark suit and derby hat.
Burt Shotton, who was the manager of the Brooklyn Dodgers in 1947 when Jackie Robinson became baseball's first African-American player, also preferred no uniform while managing (Shotton would sometimes wear a Brooklyn Dodgers team jacket over his street clothes).
John J. McGraw, the legendary manager of the New York Giants for over 30 seasons (1902-1932), wore a uniform for most of his managing career, but did wear civilian clothes for his final three seasons at the helm. These three pretty much exhaust the list of non-uniformed baseball managers.
Managers John McGraw of the New York Highlanders and Jake Stahl of the Boston Red Sox at the 1912 World Series.
The adherence to a uniform among managers in the second half of the 20th century leads some people to think that Major League Baseball mandates it. But a look at the official Major League rules doesn't turn up much.
On a manager's dress, rule 1.11 (a) (1) says that “Players on a team shall wear uniforms identical in color, trim and style, and all players uniforms shall include minimal six-inch numbers on their backs.” Rule 2.00 gives a rundown of the manager's role and some rules that apply to them, it doesn't specify that they're uniformed.
Further down, rule 3.15 says that no one is allowed on the field "except players and coaches in uniform, managers, news photographers authorized by the home team" and a few select others. Again, nothing about managers being uniformed.
All that said, rule 2.00 defines the bench or dugout as "the seating facilities reserved for players, substitutes and other team members in uniform" and makes no exceptions for managers or anyone else. This definition would seem to necessitate, in a roundabout way, that managers must wear a uniform, at least if they want to have access to the dugout. And really- where else would they sit?
It would seem that the baseball manager's uniforms are one part tradition and one part careful reading and a "just in case" interpretation of the rules.