In 1970, just prior to the merger of the National Football League and the American Football league, the NFL announced that one extra "wild card" team from each conference would be invited to enter the playoffs. In 1978, the number of wild card teams invited to the playoffs from each conference was raised to two. Twelve years later, in 1990, two more teams from each conference were allowed to play in the playoffs' opening-round wild card games.
The main benefit for the NFL in adding more teams to play in wild card games is the increase in revenue. The NFL is the most-watched professional sport in the United States. Television revenue is a big source of income for the league. By adding extra wild card teams and extra wild card games, the NFL has allowed itself the opportunity to make more money because networks are willing to pay big money for the rights to air playoff games--including the first-round wild card games.
Entering the playoffs as a wild card team puts the team at a disadvantage because it will likely not play home games during the playoffs. In order for a wild card team to make the Super Bowl, the team must win three straight road games. Between 1970 and 2008, only nine wild card teams have made it to the Super Bowl. Five of those teams have ended up winning the championship.
Some of the teams that have emerged from the NFL wild card games during the opening week of the playoffs have become some of the most memorable teams in the history of the NFL. The Buffalo Bills defeated the Houston Oilers in a wild card game in 1992 that became one of the greatest games in NFL history. The Bills trailed 35 to 3 at halftime, but stormed back in the second half to stage the most significant come-from-behind-win in NFL history when it won 41 to 38 in overtime. The 2007 New York Giants, another wild card team, made it to the Super Bowl and ruined the New England Patriots' shot at an undefeated season by defeating them to win the championship.
It should not be assumed that wild card teams are automatically inferior to division winners. Although the wild card teams are not division winners, they very often have better regular season records than some of the division winners. For example, a team in a weak division could win a division title with a 9-7 record. However, a team with a 14-2 record would be seeded lower than them if there happened to be a team in their division that went either 15-1 or 16-0. It is not always a surprise to see wild card teams beat division winners in the wild card games.