老 before surnames shows familiarity and respect among peers: 老王 (Lǎo Wáng), 老李 (Lǎo Lǐ). It's used for people of similar or older age — never for someone much younger than you.
culture
In Chinese culture, being 老 (old) is traditionally associated with wisdom and respect, unlike in some Western cultures. 尊老爱幼 (respect the old, love the young) is a core value.
