Corrosion isn't as large an issue down here for aluminum as you would think. There are a lot more aluminum boats than you are giving credit also. Xpress, G3 and a few specialty brands of aluminum bay boats are pretty popular...but I do agree that there are far more fiberglass boats.
I know in the PNW, aluminum is somewhat considered THE boat material. Down here, people generally look at aluminum boats as "economy" grade. Its what you buy when you can't afford the fiberglass boat you want.
And for offshore, there really aren't any manufacturers that cater to the "~25ft and up" center console crowd. Metal Shark is about the only manufacturer I know that offers a true offshore fishing platform but they are a specialty / custom manufacturer.
Going back to inshore, which is where you will see a mix of aluminum hulls in the crowd, the biggest thing I have noticed when fishing in closer quarters, bayous and even sight casting is the noise is much more difficult to overcome in an aluminum boat. My father fished an 18ft Alumaweld modified v-hull for about a decade. I ran a 20ft Seachaser Flats for about half that time. We both loved fishing the bayous and oyster flats for specs / reds. As soon as I bought my boat and we had some overlap fishing together on each boat, it was obvious how much quieter the fiberglass hull was. Not just noise inside the boat (setting stuff down, accidentally dropping something, stepping up / down from decks) but the constant lapping of water against the hull made SO much more noise against the aluminum hull than the fiberglass hull.
And as MadMooner stated, aluminum is a great heat conductor when the Gulf Coast sun has been beating directly down on it all day. We learned real quick in dad's Alumaweld that you didn't sit down on the bare aluminum in the spring or summer without a cushion under your azz.
Now, get north of the coast just a little bit and the duck hunting crowd will start to offset the trends a bit....they love their aluminum boats and gator tail / mud devil motors.
