How Japanese communicate differs drastically from English-speaking people. It's partly cultural, but largely, in my opinion, because of Japanese language grammar. For instance, you say in English,
"I don't like apple the most among fruits."
In Japanese, though, for a direct translation,
"I among fruits banana the most like not."
As you can see, the verb comes to the last in Japanese. Also, you don't know whether "I" like banana until the end. What could be the significance of such grammatical structure? One thing I can think of is the "time".
Obviously, you have more time to convey your true intent when you speak in Japanese. The time you "earn" while your true intent is being conveyed allows you to see a listener, and his/her reactions, such as eyebrow movement, smile, body movement, etc., enough to portend what your listener will think of your opinion as to whether you like banana or not.
For example, you are saying the sentence up to "banana" and see your listener smiling. Then, you feel that the listener like banana. But what if you are to say you don't like it? If you are very close to the listener, you may be worried that the fact that you don't like banana may militate against the relationship with the listener because you fail to show commonality.
What then? What if you care so much about your listener's feeling about banana? What if you are in a sensitive position where you must not hurt your listener's feeling? What if you are pining for sharing your penchant for banana with your listener? What if it's gauche to have any disagreement in a liking for fruit? The easiest solution is to omit "not" that comes last. Such extemporaneous action can be taken only if the sentence is structures such that your true intent won't be expressed until the end.
Japanese have a natural disposition to show empathy. That's partly why Japanese nod constantly during conversation. When Japanese tend to feel uncomfortable in a situation without communality or solidarity. Then, Japanese tend to either consciously or unconsciously ingratiate themselves by showing empathy. Whether removing "not" in the end is part of the disposition and, in a way, a strategy to promote harmony. It may look too canny or too timorous or too tedious to do such things. But that's how Japanese communicate whether you like it or not.