Lee includes this little detail to emphasise the overall picture of Judge Taylor as a very human man, despite his elevated status. Rather than portraying him as an dread figure of authority, Lee stresses his warmer, more personal side throughout:
He was a man who ran his court with an alarming informality—he sometimes propped his feet up, he often cleaned his fingernails with his pocket knife. (chapter 16)
These little personal details, this picture of his ‘informality’ all help to make Judge Taylor a more sympathetic and likeable figure.
The fact that Judge Taylor and his wife don’t kiss much is also due, it seems, to his deplorable habit of chewing on cigars. However, this specific reference to the lack of sensual contact with his wife also underlines the fact that he is a tired, ageing and ultimately rather ineffectual man, despite his position of social authority. Scout realises just how weary he looks at one point during the trial. His appointment of the eminently fair-minded Atticus to defend Tom Robinson indicates his desire to see real justice done, but in the end he will be powerless to overrule the racial prejudice of the jury who will convict Robinson solely on the colour of his skin, and in the face of opposing evidence.