Anyone ever notice that even in many locales where it is illegal to drink in the park by statute, its enforced sporadically at best as if its not a high priority? Well that's because its not a high priority.
Take that for what its worth.
True, and my guess is that either it really is low priority, or the "no alcohol" rule is to discourage public drunkenness. Just as it's easier to convict someone for an open container than drunk driving, it's easier to charge a drunk with possession of alcohol in violation of the rules. A lawyer can blur the lines and argue that someone wasn't really drunk, but it's harder to argue that the alcohol wasn't alcohol.