The stadium for a Super Bowl is an after thought. The ability of a city to host the Super Bowl for week leading up is the biggest thing. Giving the SB to cities with new stadiums is just a reward to those owners and tax payers for shelling out a billion dollars.
This is evident by the fact that Miami has continued to get Super Bowls that stadium is an absolute dump but the city can host well.
The nfl gives the SB as a reward for spending money not because your new stadium is so super cool and has WiFi.