First, show you are going to have an opportunity to compete for playing time. That helps get some better depth within classes through recruiting. Second, play a lot of guys in games. Obviously this builds depths in multiple ways as others have said. The unheralded advantage of that if you have 16-17 guys that are likely to see the field on defense as part of typical rotation rather than 12-13, you have more guys fully engaged in practice and meetings. Not only are more guys playing, a guy that may have been two or three injuries away from seeing the field might be one injury away. It reminds me of something Chris Peterson said when he was at BSU. He played a ton of guys and would always have weekly packages and series where backups and third string guys played and even got the ball. He said whatever dropoff he might have in talent on the field for a few plays each week was more than offset by having a lot more guys all-in and fully engaged in prep every week.