Why do they put etymologies in general-purpose dictionaries? I certainly don’t need them.
Because they explain why the word means what it means and it can help you figure out the meaning of other words.
One of the things we learned in Spanish class (Spanish being my first language) was “word roots”. When I took the GRE and the TOEFL, there were a few words which I hadn’t encountered before but, since I knew their roots, I knew instantly what they meant. Etymology thus helped me get into graduate school.
Um…because they didn’t make a version of the dictionary just for you?
I wanted a version of the dictionary that just had etymology and pronunciation, but no definitions; turns out they refused to crank out that version, too. In their infinite business wisdom, publishers decided that the best revenue model was based on publishing just one version of the dictionary that has all of that info in it.
Well OK, two versions, if you count “abridged” and “unabridged.”
You certainly can get dictionaries without etymologies, but they’re generally cheap ones. A dictionary is a work that does many things, and etymology is one of them.
Johnson’s Dictionary in 1746 wasn’t the first, but the previous one were really just lists of words. in 1583, Richard Mulcaster, a headmaster compiled what he termed “a generall table of words we commonlie use”, but a list like that is not really much use, except for scrabble players.
Since Johnson, there have been many thousands of dictionaries with different emphasis. I think is it universally acknowledged that the Oxford English Dictionary (first published only a century ago) is the largest and most comprehensive.