That’s why you build them with the seats covered, field uncovered.It's a business decision. The nicer the conditions inside the stadium the higher the demand for tickets and the more you can charge. On the cost side roofs are expensive to build and costly to maintain. Stadia have to be multi-purpose because 9 NFL games per year for 30 years isn't going to justify the cost.
If it were that simple there wouldn't be any NFL domes.That’s why you build them with the seats covered, field uncovered.