There's no reason for manual really unless you do races or don't want to pay premium for auto. As I understand, there's no financial disincentive for automatic in America, hence most opt for the most convenient option.
And it's just more fun to drive when you have complete control of torque going to the wheels under your right foot :)
I've raced my brother-in-law out of red lights a few times, him in a Nissan Leaf, me in a Peugeot 307 with a 1.6 110 hp petrol engine. I can keep up, but I have to stay above 3000 RPM throughout all gear changes, so it's really loud. Most people never drive a petrol car like that, you sound like an idiot boy racer.
Lower maintenance costs are usually mentioned as an advantage of manual over automatic, but slushboxes have been around for quite a while now. With routine maintenance and average use (meaning no launch control usage or burnouts), both types will last forever.
Fortunately the fun factor has gone up by the same amount so I don't care...
Mostly though, I just enjoy the nearly zero maintenance (check fluids regularly of course, change clutch every 10 years or so) that a manual provides on an older vehicle. On newer vehicles like my Crown Victoria or my wife's Nissan Versa, the automatic just makes more sense. It's just as dependable as a manual, and only slightly more frequent maintenance (60k mile service intervals on both cars).