Why learn the words you use?

I have to admit that nothing irks me more than browsing through the Official Scrabble Dictionary (which I will refer to as The Dictionary) and finding words that don't really belong.

Scrabble is supposed to be a game of English words and loan words.  "Loan" words are words that are in common usage throughout the US and England.

Here in the US we have a lot of loan words from Spanish. (AMIGO for friend, for example), and British English has a lot of loan words - or perhaps "loan spelling" would be a more accurate term - from Scotland (SAB for SOB for example). 

But CAHIER?

CAHIER is French for "notebook"...and the only people who use CAHIER on a regular basis are the 1,000 or so intellectual film buffs in the US and England who read the magazine CAHIERS du Cinema. No one else would know this word because it simply is not in common usage...so it does not belong in The Dictionary, in my opinion. If you're going to use CAHIER then why not use "cuaderno", which is Spanish for "notebook"?

I'd love to be a fly on the wall of these "Let's Add New Words to The Dictionary" meetings, just to find out their reasoning behind why some words are included and some words, which you would think would be included based on other words of a similar nature that are included, are not.

For example there are a few names of runes which are included in The Dictionary, and others aren't.  Why not? If you're going to include a handful of very-rarely-used words for certain runes, why not stuff that hand full with all the words for runes?

Why learn the words you use?

Having said all the above, it is interesting to go through The Dictionary and learn the meanings of all these words. That's one of the benefits of Scrabble - or should be - to improve your vocabulary, even if you're learning words that you'll never use in your life outside the Scrabble hall (which, as an aside, is why spelling bees annoy me. Test people on words that they need to know, not on words that they will never, ever ever use...)

I also think it's a lot easier to remember words if you know what they mean - and it's important to know what they mean if you want to be able to conjugate them or pluralize them.  (Can you put an S at the end of QUA?  Why no, you can't.)

So learning the word definitions makes sense.