With a limit of 24, it means the AUS can still say they have a 'Limit', but it's effectively high enough that no one will complain. So, they don't have to deal with griping and complaints anymore.
You can only dress 20 (18 skaters and 2 goalies), so you would have 4 skaters in the stands if you max'ed out and everyone was healthy. Having access to 3-4 players versus 2 is a big deal and gives coaches the opportunity to take a flyer on a Jr. A player who can be on the Taxi squad until you need him (an approach that ended with the 22 cap).