Laura Miller says here that 

Tolkien himself admitted to a correspondent that Tom is “not an important person—to the narrative,” but then, crucially, he added that Tom does represent “something that I feel important, though I would not be prepared to analyze the feeling precisely. I would not, however, have left him in, if he did not have some kind of function.”

Tolkien resisted explaining Tom … 

Well, not really. If she had kept quoting the letter that she was quoting — a very long April 1954 letter to Naomi Mitchison — we’d have seen: 

I might put it this way. The story is cast in terms of a good side, and a bad side, beauty against ruthless ugliness, tyranny against kingship, moderated freedom with consent against compulsion that has long lost any object save mere power, and so on; but both sides in some degree, conservative or destructive, want a measure of control. but if you have, as it were taken ‘a vow of poverty’, renounced control, and take your delight in things for themselves without reference to yourself, watching, observing, and to some extent knowing, then the question of the rights and wrongs of power and control might become utterly meaningless to you, and the means of power quite valueless. It is a natural pacifist view, which always arises in the mind when there is a war. But the view of Rivendell seems to be that it is an excellent thing to have represented, but that there are in fact things with which it cannot cope; and upon which its existence nonetheless depends. Ultimately only the victory of the West will allow Bombadil to continue, or even to survive. Nothing would be left for him in the world of Sauron. 

Which is a very revealing, very helpful, and very “explanatory” comment. 

The Rings of Power really does sound like a terrible show. I haven’t seen a minute of it.