Why is that a good thing if your italian boyfriend doesn’t tell you “I love you”

During a farewell party at Disney, a Japanese girl asked us why her Italian boyfriend, who she had been knowing for just few months, didn't tell her "I love you" yet. She was very worried, and she feared that he didn't like her for real. Explaining her the reason of his behaviour - which, for us Italian, was completely normal - wasn't easy, and translation is to blame.