Because it is. The two best teams in the Majors.
Except that they both have lesser records than the St. Louis Cardinals.
Sometimes, records can be misleading. Take a look at the 2000 Yankees. Plus, the Cardinals don't have to play Boston or NY like 19 times a year.
They also don't get to play tee-ball with Toronto or Baltimore 19 times a year. And it's not like the NL Central has been a complete joke either, with Chicago and Houston battling for the wild card.
I think the Brewers, Pirates and Reds are worse than the Orioles and Blue Jays.
The Astros have sucked all year till this last month, and the Cubs are a team in limbo that have had injuries all year.