Many times in new stadiums tailgating is discouraged or prohibited all together. Or they will greatly limit the tailgating area.
One reason is they don't want drunk fans coming into the
new stadium starting fights.
Another reason is the NFL wants a wholesome experience so a family of 4 can enjoy the game without running into drunks who are starting fights or cussing in front of children
Of course another reason is fans are forced to buy expensive concessions