^ what are they gonna do, randomly punch you in the face in front of a crowd of people?

They might do. They might also:

• wait until closing time and then follow you home, sparking a months long campaign of stalking and harassment
• spike your drink and steer you away from safety when they get a chance Amongst other things.

“I bet the person would walk away willingly”

A reasonable person would, but the danger here is that the prevalence of unreasonable people who would respond poorly to being rejected is high enough that it is necessary for women to build systems like this to keep each other safe. You’re right, that this system is to compensate for a lack of social skills, but it’s compensating on behalf of petulant men who refuse to take no for an answer.

If this sounds absurd to you, congratulations, you’re probably a reasonable person who would respond rationally to being rejected, but most women I know have had bad experiences like this. If your instinct is that this sounds like an unreasonable amount of effort to go to to avoid confrontation, consider what level of conflict has led to the formation of these practices - they don’t just come from nowhere