I think the problem is that teams want to host their own outdoor games, so they're reluctant to agree to be the visitor for one for fear of moving to the back of the list. As a result, we keep getting stuck with Chicago and Detroit every year.
After next season, there will only be 7 teams who haven't yet played in an outdoor game:
- Arizona
- Carolina
- Columbus
- Dallas
- Florida
- Nashville
- Tampa Bay
Also, Anaheim, Ottawa, Montreal, and the Rangers have been in outdoor games without being the home team. The Rangers played two games at Yankee Stadium as the road team and the Ducks were the road team at Dodger Stadium, so at least their local fans were able to go to the games if they wanted to without significant travel.