Why do NFL stadiums do that?? Limited tailgate time.

I had four USAF buds fly into town to see the Rams / Jags game in 2017. We had planned to make a full day of the 4:20 PM start BUT NOOOOOOOOOOOO. We could not park till just four hours before kickoff. By the time you park and get set up, almost 30 minutes has already been killed. THEN, you have to start packing up well before kickoff to get everything put away and get to your seats. To be frank......IT SUCKS!! Tailgating is an American past time, DAMMIT!