We travel between twice and three times a year to the Caribbean and have been doing so for years. The flight between Miami and St. Vincent & the Grenadines (our last three flights) is usually a 737.
Main cabin extra is a recent name for something AA has pretty much had for years now. Basically, you pay extra for bulkhead seats. The free drinks thing is new but frankly, we don't drink on flights anyway. Sodas are free no matter what seats you are in. But I'm six foot two (about 220) and the extra leg room is worth it on the 4 hour plus flights. Obviously "main cabin extra" includes more than the bulkhead seats...so AA can make more money. But those are the ones you want. The main advantage with bulkhead seats is that there is no one in front of you to suddenly decide to fully recline their seat.
When we can, we always fly front row business class. But AA has dramatically raised the price to our favorite destinations (SVD, UVF, BGI) and what was once between $2100 to $2500 for two non-refundable business class tickets is now $3700. And they will TRY to get you to bite on a $5200 price tag. I don't know exactly how that works but when trying to book ten months in advance, the first price is always $5200. We wait a couple of months and the price generally comes down to the $3700 we will pay. If not, we just book main cabin extra and pay for our bags. It runs us about $2500 total during high season.
Look...AA is just another giant US corporation. They want to get as much of your money as they can while continually telling you how wonderful they are. But they are not in business to do you, me, or anyone else any favors because they somehow "like" us. They don't treat the people who work for them very well...why would they somehow treat us better?
We fly AA to our Caribbean destinations not because we want to but because we have to. With Miami as their Caribbean/South American hub, they have the best arrival and departure schedules to and from the islands we visit. I've looked at Delta connections out of Atlanta (which are generally cheaper) but I can't seem to make them work for us.
When we lived in Chapel Hill, NC we could fly AA direct out of Charlotte, skipping Miami entirely. We miss that a LOT!!!