1. Content has to be put into DF at some point, having 8 ppl instead of 24 means faster queues. See what happened with CT 1 before they did the weekly quest. DF was never able to find more than 12 guys.

2. 24 man raids require more design. And making a difficult 24 man fight seems not easy. We never seen a "hard" 24 man fight. I cant imagine a FCOB "24" without a big mess or at least a lot of work for the devs.

3. Not every FC has 24 raiders. 8 was appropriate because even small FCs with 6 ppl were able to pick up a couple of fillers and go. A 24 man raid will prevent a lot of small FCs from raiding. Or force them to merge / change the way they want their FF experience just to be compliant with the raid format. Being social is part of a MMO, but if you prefer 10 ppl FCs its fine. Especially if you re from a small community like those finnish or greek FCs we have here. You shouldnt have to be in a big FC (big enough to have 24 raiders at the same time) to enjoy FF14.