Kissing goes by favour.

At its most immediate, the saying presents a kiss as something bestowed where there is liking. Affection is not distributed automatically; it follows the goodwill or preference of the person who gives it.

More generally, it says that desirable favours, opportunities, and access may depend on personal preference rather than desert. The image of kissing makes a broader point about partiality deciding who receives an advantage, often critically depending on tone and context.

Use it when remarking that a benefit, welcome, appointment, or other advantage is awarded through personal liking rather than solely through merit. It can be said critically of favoritism or simply as a resigned observation about how preference operates.