In the 2018 NFL regular season, teams occupied each record from 13-3 down to 3-13, except one. The four teams that played to a tie finished 9-6-1, 8-7-1, 7-8-1 and 6-9-1, clustering around .500 ball.
No team actually finished 8-8, despite it being, by definition, the league's average record. Every team had either a winning season or a losing season.
Past seasons' standings have seen notably absent records, like the curious lack of 12-4 teams last season despite three teams being 12-3 (Patriots, Steelers, Vikings) and another three teams being 11-4 (Panthers, Saints, Rams). This season, the only 8-8-eligible teams heading into Week 17 were the Eagles, who won in emphatic defensive fashion to win 9-7, Washington, who took a 7-8 record into that same game, and the 7-8 Miami Dolphins. The Arizona Cardinals were the only NFL team to finish 8-8 last season. With only one 8-8 team in the past two seasons, this is either a trend toward more complete rebuilds (as there's no reward for barely missing the playoffs), or it could just be random noise.
This is the first time no team has finished 8-8 in the history of the 16-game season. No team finished with a .500 record in the shortened seasons of 15 games (1987) or nine games (1982), but that is easily explained by both seasons having an odd number of games, meaning a tie would be required to play .500 ball. Even then, in each of those seasons, there were nine teams within one game of a .500 record. The previous high is nine 8-8 teams in 1999.