Quote Originally Posted by DrNewGod View Post
Just guessing, same reason as Green Arrow and the rest of the Seven Soldiers.

In its first few years, All-Star Comics was kind of a launching pad for properties that could not only anchor an anthology book, but headline a title book, like Superman and Batman. When they were getting close, they became the Chairman, and then got promoted out (Flash and Green Lantern; I have heard Hawkman was next, but WWII paper rationing made it unfeasible). When characters' popularity dropped, meaning a solo wasn't even possible, they were cut from the team (Hourman, Dr. Fate, the Spectre). Now, by mid-WWII, the rules had changed, and the roster was set in stone. The only roster change was Black Canary, who replaced Johnny Thunder in both the JSA and his feature in Flash Comics.

Aquaman didn't hold a title until the late 1960s. So, like Johnny Quick, Robot Man, and The Seven Soldiers, I'd guess he just didn't show the support to put him in contention for a title during that formative period of the JSA.
I've always been intrigued by that aspect of a book filled with contenders, but the second they become a champ, they're out, or relegated to guest appearances. It's completely counter to the way these things work now, where nearly every new Justice League iteration, Batman at least shows up, because his popularity makes him a selling point.

Now obviously this isn't universal - many teams like the contemporary JSA, the Legion of Super-Heroes, the All-Star Squadron, etc. tend not to have many or any characters who have their own book outside the team! But the Big Teams, the Justice Leagues - which the JSA was at the time - generally has only a few members, like J'onn J'onzz or Cyborg, who struggle to keep a regular title.

I mean I guess all that goes without saying but heck if I didn't decide to up and say it anyway for some reason.