Time and time again, the Ravens have shown that they are dedicated to their players. It seems as if many of the Ravens' greats stayed with the team for almost the entirety of their careers. Ogen, Lewis, Reed, Stover, and plenty of others all spent the majority of their careers in Baltimore. This loyalty from both the team and its players has made Baltimore one of the more attractive destinations for players both young and old.
Among current NFL rosters, the Ravens are near the top with nine players on their roster last season that had been with the team for more than 5 years. This is according to Redditor /u/ehoefler.
Flacco, Pitta, Yanda, Suggs, Webb, Smith, Koch, McClellan, and Cox have all been with Baltimore for half a decade or more. This puts Baltimore in the top half, behind league leaders Cincinnati and Green Bay with 18 players each.
The interesting trend is that player continuity correlates with winning games.
The teams that retain their players for longer also happen to win more games. The practice of keeping players around for the long haul is something that the Ravens have done for a while, and perhaps it explains their tendency to win.