The first NBA game played on December 25 came in 1947, a year after the NBA’s Beginning, when the New York Knicks beat the Providence Steamrollers at Madison Square Garden 89–75.

Ever since then, the NBA has played games every year on Christmas Day except in 1998 (if a lockout canceled half of the 1998–99 year ). By comparison, Major League Baseball is at its own off-season during Christmas, the National Football League only programs Christmas games when Christmas falls on the weekend (and even then just schedules games on Christmas occasionally) and the National Hockey League’s collective bargaining agreement forbids playing matches on Christmas Day (and, except when it falls on a Saturday, Christmas Eve as well). In college football, the only bowl game traditionally scheduled for Christmas has become the defunct Aloha Bowl (and for one year, its replacement, the Hawaii Bowl). Thus, the NBA is the only league.
In the first days proximity dictated most of the matchups. Teams would usually play their geographical rivals to cut down on holiday travel and also to allow them to have additional time with their families. According to Dr. Jack Ramsay, who coached the Portland Trail Blazers from 1976–77 (their only championship season) to 1986,”Christmas supposed being at home with the family and using a match we won. This was a perfect Christmas to me.” He set the record for most coaching victories on Christmas Day with 11, an accomplishment that Phil Jackson afterwards matched in 2008.
In the 1980s, the New York Knicks put three years in a row. In one game (1984), hall-of-fame forward Bernard King scoring 60 points–the most ever scored by a player on Christmas Day, With the dawn of television and the excitement brought on by these games, the NBA decided to scheduled games over the holiday that showcased the best teams and players.

Read more: https://montanayouthrugby.org/ascot-tips/