Because the SEC consistently dominates the National Championship. The conference has earned getting sucked up to. I don't think it's always been the best conference, but in the last several years, they regularly have the best team.
I personally find it comparable to Kentucky High School football. People often debate who the best team in Kentucky is on a yearly basis. Almost always, it's a 6A Louisville school. Championships speak volumes. I'm not a KHSFB expert by any stretch, but I can tell you with confidence that the best Louisville has to offer in 6A will very likely win the whole thing.
I totally understand the frustration. But College Football has always had a flawed championship system. Always. While I don't think Florida State is a Top 4 team, it's ridiculous that they go undefeated and are left out. It's happened other times too, including an undefeated Auburn being left out one season.