People skills really about a good handshake and not eating with your mouth open (although your mother was right, the aforementioned are important skills).
The underlying intent of skills like etiquette, small talk, eye contact, handshakes, smiling, etc. is far more important than these physical or practical manifestations. Interpersonal skills are the manifestation of an intent and the intent is to treat others with the same understanding, compassion, respect and positive regard as you would like to be treated.
Interpersonal awareness is based on the understanding of other people, their needs, desires, motivations, emotions and we use that awareness to make others feel respected, or acknowledged or liked or even loved.