Whether it’s the lip-smacking sound or the fact that it’s considered poor etiquette, some people consider this their biggest pet peeve.
It’s easy to see why. Chewing with your mouth open is the sort of thing most of us do as kids and either grow out of on our own or are taught to stop, so continuing to do it into adulthood can come across as childish. Some folks simply aren’t aware they’re doing it, though, and it’s difficult to ascribe rudeness to an unintentional act — especially when there’s nothing stopping you from gently putting it out rather than getting silently angry about it. As with most things, a little open communication goes a long way.