The root problem with kissing outside of marriage is that people desire love outside of marriage. Which is why dating is wrong. Love should only be in the context of marriage. As a result, kissing, hand-holding, etc. should also only be in the context of marriage.
Song of Solomon 1:2
Let him kiss me with the kisses of his mouth: for thy love is better than wine.
Song of Solomon 2:4-5
4 He brought me to the banqueting house, and his banner over me was love.
5 Stay me with flagons, comfort me with apples: for I am sick of love.
18 Let thy fountain be blessed: and rejoice with the wife of thy youth.
19 Let her be as the loving hind and pleasant roe; let her breasts satisfy thee at all times; and be thou ravished always with her love.
20 And why wilt thou, my son, be ravished with a strange woman, and embrace the bosom of a stranger?
Song of Solomon 4:9-11
9 Thou hast ravished my heart, my sister, my spouse; thou hast ravished my heart with one of thine eyes, with one chain of thy neck.
10 How fair is thy love, my sister, my spouse! how much better is thy love than wine! and the smell of thine ointments than all spices!
11 Thy lips, O my spouse, drop as the honeycomb: honey and milk are under thy tongue; and the smell of thy garments is like the smell of Lebanon.
"[W]hy wilt thou" "be ravished with a" stranger?