There are 7 referees in a game.
3 referees are in soccer and football
There can be 2 or 3 umpires for each softball game. One umpire stands behind home plate and calls balls and strikes as well as other plays on the field. The other two are the first base umpire and the third base umpire.
Four. One in the center, two assistant referees, and one fourth official.
Only one 'match referee', however two umpires are there in the field and 1 third umpire, out of the field.
Because there is more pressure on the referees from the media and managers
There are seven on field officials in an American football game: referee, umpire, head linesman, line judge, side judge, field judge, back judge. Click on the 'NFL Officials' link on this page to read about the duties that each official has during a game.