>If these were common cases, cops would lay in wait and nab them for open container.
I mean, they do. One of the big issues is coverage of enforcement. Here in Texas you see disparities where arrests in big cities converge on public intoxication, where in smaller cities you run into a higher ratio of open container because of cops having time to sit and watch stores.
The only places that sell individual beers are convenience stores
Some of them are driven too, sure, but lots are also in city areas
Even so, people who only have a few bucks drive to the store where they can buy the beer, and drive home and drink it
If these were common cases, cops would lay in wait and nab them for open container.