Why do many sports teams seem to wear white jerseys when they play a home game?

Question

Why do sports teams like baseball, football, and basketball wear white uniforms when they play a home game?

Answer 1

Why do sports teams like baseball, football, and basketball wear white uniforms when they play a home game?

In short, because they're addressed in the rules. More practically, it's to distinguish two teams from one another.

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For the MLB, the home team wearing white uniforms may be required based on the league said team is in. This is addressed in Rule 3.03(d) of the 2016 MLB rulebook:

A league may provide that each team shall wear a distinctive uniform at all times, or that each team shall have two sets of uniforms, white for home games and a different color for road games.

For the NBA, although the home team wearing white uniforms is not a requirement, it does require said team to wear light-colored uniforms. This is addressed in Rule 3, Section VI of the 2015-2016 NBA Rulebook:

The home team shall wear light color jerseys, and the visitors dark jerseys unless otherwise approved. For neutral court games and doubleheaders, the second team named in the official schedule shall be regarded as the home team and shall wear the light colored jerseys.

For the FIBA, although the home team wearing white uniforms is not a requirement, it does require said team to wear light-colored uniforms (and explicitly prefers white). This is addressed in Rule 4.3.3 of the 2014 FIBA Rules of the Game:

The first team named in the programme (home team) shall wear light-coloured shirts (preferably white).

For the IFAB, the home team wearing white (or light-colored) uniforms is not a requirement. However, it does require both teams to wear distinct colors from one another. This is addressed in Law 4, Section 3 of the 2016-2017 IFAB Laws of the Game:

The two teams must wear colours that distinguish them from each other and the match officials