Why
not Tolkien?
You say you are mainly interested in the "why", and not the "what", but I see the questions as too closely intertwined to seperate.
I am, and have been a voracious reader as long as I can remember, for thirty-odd years. I recall knowing of
The Hobbit from the time I was around five or thereabouts, read the book by my father. I'm told I went to see the Bakshi animated
LOTR movie when it was in theatres, though I was too young to remember it. In summary, Tolkien has been a part of my life as far back as memory goes. There are several reasons for the "Tokien Chord" in my case. I suppose one reason is the fact that I am something of a traditionalist, and identify with many of his common motifs in the books: honour, determination, courage, and devotion to duty, among others.
Another reason is that I am a devoted 'Anglophile', from music, to literature, to history. The English 'feel' of the works appeals to me, and I greatly doubt I would find a fundamentally identical
LOTR written by a Swede or an American to be nearly as inviting.
Thirdly, Tolkien's linguistic skills are probably what really sets his works apart for me. I've often thought that it may be the sheer delight I find in the florid and archaic prose that keeps me reading the books again and again rather than the stories alone. I simply have not found words in fiction to match the likes of Tolkien, and I doubt I shall.
For those reasons ( and I could probably come up with more), Tolkien is the sole 'fantasy' author in my bookcase.