I am only interested in teams that I follow throughout the season and I do not follow the Raiders or the Seahawks throughout the season so I do not really care what happens to either team in their last preseason game. Now if we were talking about the Green Bay Packers then I would be very interested, would watch the game, and would care a lot since that is my team.
Half the pre-season is for players to try to get noticed to avoid being cut. Most of the guys who are a lock to make the team or are already on the team aren't playing a lot so they won't get hurt. Plus there's not much correlation between a team's pre and regular season performance overall, so it doesn't count for much.
Most NFL fans do not care about the last preseason game. By the fourth preseason game, fans are ready for the regular season to start. Preseason games do not have any bearing on the regular season, so they rarely garner as much interests. Instead, fans are focused on how their team will play during the regular season.
No, the last preseason game is not that important. It's more like an exhibition game rather than a real competition. One can consider it a practice game before the season actually begins. Most people are waiting for the season to start so that football can begin in earnest throughout the United States.