Is the presence of alcohol or is it the way some people behave while drunk? Because that behavior could be illegal without being drunk also being illegal.

Put another way, people get arrested sitting quietly because they are drunk without any obvious outward signs of being drunk so it’s is hardly intimidating.

That’s because a drunk persons’s decision making is inherently impaired. They might be sitting quietly now. The vast majority of criminal violence (domestic or otherwise) occurs in conjunction with impaired faculties and alcohol is often the cause.

A classic pre-crime argument.