Good for you, on not selling American Alligators to unsuspecting pet owners... Most folks really aren't prepared for something like that. If you _are_ prepared, and capable of meeting the needs of an adult Alligator... fine. Not like they're endangered. They're not my idea of a good pet, but to each their own. I've known people with adult black caimans that were quite successful with them, and enjoyed keeping them.
I will say, however, that Anaconda don't really fit into the same category. You can successfully keep an Anaconda in a cage no bigger than the likely 'average' sized aquarium for folks on this site. They're not hard to feed, unlikely to injure an adult keeper... beautiful, interesting... I've kept large pythons, and enjoyed having them as a pet. I've also kept (and bred) large Varanids (Nile and Water monitors). Much more of a challenge. I quit keeping large reptiles when my first daughter arrived... having a creature in the house that would be happy to eat our newborn, given the opportunity, was somehow upsetting to my ex-wife. Go figure ;)
Need? None of us here, excepting perhaps a few of the scientific types doing research, have any demonstrable 'need' for keeping marine aquaria. It's a hobby. Keeping large reptiles is also a hobby. In a free society, you don't have to show 'need' in order to pursue your dreams.