Why do people tend to focus on your lips when talking to them with earphones in ?

Just a bit of a bored musing for a December evening 😃

I've noticed that when I'm being served in a shop for example and I'm wearing earphones (I often take one earphone out) people focus more on my lips when I'm talking as opposed to my eyes when I haven't got earphones in.

I've casually wondered why this is as the person I'm exchanging a few words with can still hear me as they haven't got earphones in & my earphones don't affect my speech.

Eyes and lips are natural focal points I suppose.

I've realised I may have a tendency to do this too if someone I'm talking to is wearing earphones but why is this ?

😃