The censors objected
Donna Reed and James Stewart
James Stewart (May 20, 1908 – July 2, 1997).
James Maitland "Jimmy" Stewart was an American actor. Known for his distinctive drawl and everyman screen persona, Stewart's film career spanned 80 films from 1935 to 1991. With the strong morality he portrayed both on and off the screen, he epitomized the "American ideal" in the twentieth century.
James Stewart was reportedly very nervous about the phone scene kiss in It's a Wonderful Life, as it was his first film since he had returned from the war. He filmed the kiss in one take and enjoyed it so much that part of the scene was cut as it was far too passionate to pass the censors.