And those stories would be nothing without the second World War. Which is real world continuity.
Canon doesn't just apply to fiction. You can't just make up a fake war in the real world without breaking verisimilitude. There's just as much research required.
Can't you?
It's notorious that the whole premise of Casablanca is nonsensical (the "Letters of Transit", signed by General deGaulle, are an imaginary form of travel document that, in any event, could simply be cancelled).
And the image of Morocco was purely fictional, conjured up in a Hollywood lot.
So that's fake documents and fake geography. As for fake wars, I've seen plenty of action movies that present accounts of paramilitary activities in (say) Central America that bear at best tangential connection to the actual events in those countries.
If a typical present-day American came across a story set in the 1910 war between Bulgaria and Romania, would s/he know whether or not it was a real or fictional war? What sort of weaponry or tactics might be mentioned without breaking verisimilitude?
In my Marvel Heroic RP game, the PCs infiltrated the Latverian embassy in Washington DC. Where is that again? (The embassy? The country? Both made up, and trading on the fact that the average comic reader is largely hazy on the details of Central and Eastern European geography and history.)
One of the strengths of those books is the sense of history and the larger world. The feeling that the storyt is just one of many. Hence all the poems and songs and side stories sprinkled through the works. The hints of backstories.
That makes the books.
But does not depend upon "canon". You can do all that without Appendix B. And Appendix B itself changed between editions, I think (Unfinshed Tales talks about this).
The Hobbit was itself revised, multiple times - and ret-conned (the original version was "a lie" by Bilbo about the true nature of his acquisition of the Ring) - to bring it into line with LotR.
In other words, JRRT didn't just stick to his established continuity - which is to say, by your standards, he sucked as a writer!
You want books without continuity that do their own thing.
I want books with continuity that respect what's already been published.
You can ignore continuity that is there. That's zero work.
I can't easily add continuity where there is none. That's a lot of work.
But I don't want books that I am going to ignore. If I'm going to buy books, I want to use them.
Which means I want books with compelling stuff in them. If sticking to "canon" is an obstacle to that (which, clearly, it can be - qv Planescape) then we can't both get what we want.
At that point, your preferences have no moral priority over mine.
(This point has been made very many times already in this thread, by me and by [MENTION=22779]Hussar[/MENTION], but it seems to need reiterating every 50 posts or so.)