I think the problem most people have with this is traffic. I'm with you (and I'll preface this with I'm very old and would NEVER have thought this was in my twenties), I would rather sit in the air conditioning and chill and watch other games and drink and take a nice stress-free, non-Porta potty or into someone's open truck door ****, and then go to the game. The problem is, let's say it's an 8:00 game. If you want to do what I described above, you probably need to leave that establishment at 7:00 to get over to the game. And that last hour of tailgating is when everyone really starts foaming at the mouth and things start to get wild. I don't want to be sitting in a car, or an uber, in traffic going 2 mph trying to get into the stadium in that situation. I'd rather already be at the stadium and I can walk in when I want.
I think in a lot of other stadiums, it's either on campus, or close. So you can do what you're describing. Go sit at a bar a few hundred yards from the stadium and walk over when you want. You can't do that at Hard Rock. So I'd rather get there maybe 90 minutes before kickoff, get a nice lather in, and then walk in when I want vs the anxiety of battling traffic at 7:30 with a nice buzz wondering if I'm going to be able to get through this sea of ******** in time for kickoff. JMO.