Why does the NL have better stadiums?

Target Field and Yankee Stadium have something in common. They’re the two newest ballparks in the American League. In fact, they’re the only AL facilities built within the last decade. Bycontrast, the National League is full of gleaming new arenas. When it comes to state-of-the-art ballparks, the Senior Circuit is actually ahead of its time.
The Miami Marlins are opening up a brand new park this year. When the first pitch is thrown there, it will join Citi Field (Mets), Nationals Park, Busch Stadium (Cardinals), Petco Park (Padres), Citizen’s Bank Park (Phillies), Great American Ballpark (Reds), Miller Park (Brewers), PNC Park (Pirates), Minute Maid Park (Astros), and AT&T Park (Giants) among the 11 NL stadiums built since 2000. In the AL, aside from Target Field and Yankee Stadium, only Detroit’s Comerica Park has opened since then. Colorado’s Coors Field was built in 1995, which makes it the third oldest stadium in the NL!
The NL probably leads in stadium quality as well. Having lived in Northern California for the past decade, I can vouch that AT&T is a beautiful facility and a great place to watch a game. I’ve been to Pittsburgh’s PNC Park as well, and I think it might be the best stadium in all of baseball. You haven’t lived until you’ve had a sandwich and a few Iron City beers at Primanti Brothers and walked across the bridge to a Pirates game. On the other hand, some of the worst stadiums in baseball are AL parks. Tropicana Field is a notoriously non-fan-friendly dome. Rogers Centre was considered a state-of-the-art stadium of the future when it opened as Skydome in 1989, but now it looks silly and artificial compared to the newer parks that emphasize the beauty of the outdoors. Oakland’s Coliseum is as unpleasant a place to watch a baseball game as AT&T is pleasant, and it’s ridiculous new name (“O.Co Coliseum”) suits it.
To be sure, even the AL has a few stadium gems. Fenway Park, opened in 1912, is as beloved and cherished a part of the game’s history as Wrigley Field, which opened two years later. Progressive Field in Cleveland is a comfortable and beautiful facility – even when the Indians aren’t winning enough to draw a crowd. And Target Field gets unanimously great reviews, other than the argument about the trees.
It’s strange, though, that one league is filled with shiny new parks while the other’s stadiums are almost all a generation older. I’m not sure what the significance is – it’s just something that occurred to me that I wanted to discuss.