Not that I admit anything . Rather correcting thing so you do not pass for someone dishonest intellectualy. Which you obviously are .I appreciate you admitting you have a simple little mind, but again the "good reason" is that Tolkien left the world he created vague enough for that diversity to exist (while also being specific about it not being all white).
When interviewed for the Daily Telegraph Magazine in 1968 he was specifically asked if Middle-earth corresponded to Nordic Europe. Nordic Europe being the Northwestern and Northern parts of Europe, encompassing peoples such as Anglo-Saxon, Germanic, Scandinavian, Northern French, and Celts, and Nordicism being the idea that these peoples, and by extension the white race, was superior and sacred. Tolkien wholeheartedly denied these ideas and his response was as follows:
Not only did Tolkien reject the idea that the North-west of Middle-earth (where all these stories take place) was equivalent to white Northern Europe, he also didn't specify the skin color of dwarves (at all), the only reference he made to hobbit skin tone was that Harfoots (the most common type of hobbit) were "browner of skin" than Stoors and Fallohides, and Numenorians were culturally most similar to ancient Egyptians (a people that encompassed a variety of skin tones).
The idea that all these races and peoples were white is purely assumption based on Tolkien's descriptions of specific people ONLY. There were a lot of people and subgroups of people that Tolkien never gave detailed descriptions of, and he made it crystal clear that Middle-earth (from Hobbiton to the Mouth of Anduin) was not spiritually, geographically, or culturally the equivalent of white Northern Europe.
But yeah, you keep fighting the good fight for the pure white, northern European Middle-earth that Tolkien expressly said was not a thing.