I think that a lot of people view "tailgating" as being outdoors - grilling, games, drinking, music, etc - not going to a bar or restaurant.
You can go to a bar or restaurant any day of the year. there are only 7 days a year with Home gopher football games, so I think some people are hoping for something different/more special than just going to a bar. Something that is tied specifically to Gopher Football - a real "Gameday" atmosphere.
Granted, there is an opportunity for bars and restaurants to grab some of that business by trying to create a tailgate atmosphere and marketing themselves as the "unofficial Gopher Tailgate" spot or something like that. But I still think people see 'tailgating' as something different.