I get the feeling that the NFL's Top 100 players list to some extent reflects a bias of the voters for the era of football when they became involved in the sport.
Example: Of the seven defensive tackles chosen to the NFL 100 all-time team, six played in the 1970s.

So far they've unveiled the all-time running backs, linebackers and defensive linemen. No active players have made the list and only one who played in this decade (Ray Lewis, retired 2012) made it. Also none from the 1920s. It's supposed to encompass all 100 years of NFL history.

Here's how many players were active during each decade among the RBs, DTs, DEs and LBs on the NFL all-time team:
1920s: 0
1930s: 2
1940s: 4
1950s: 7
1960s: 13
1970s: 17
1980s: 14
1990s: 10
2000s: 7
2010s: 1