"12 Letters That Didn't Make the Alphabet," appeared in the The December 13, 2012 edition of Mental Floss. It should be required reading for everyone who loves language and its history. Do read it, and as you read, think about the reasons we still might encounter these graphemes as well as why we no longer teach them to children learning their ABC's.
M. Asher Cantrell gives us a look at letters/graphemes that have been discarded for a variety of reasons. For some, type setters found substitutions, but we still see them in specific situations. For example, if you have been to Williamsburg or watched movies set before the American Revolution, you will see the thorn in signs (for example, Ye Olde Tavern). While the thorn looks like a "Y," it should be pronounced with the strong "th" sound that appears at the beginning of its name. In this case, the language was becoming more streamlined. Printers didn't need to include another letter in their type drawers, but they were still able to convey the sound without any confusion. That is, they didn't have confusion back in the old days. Now, as often as not, people will pronounce the thorn with a "yuh" sound and say, "Yee oldeee tavern" and think they sound literate.
Some of these characters are still in use, but they are not included in our recitation of the alphabet song, the ampersand (&), for example. It was the final letter of the alphabet before it was cast aside. Then, as now, "&" meant "and." According to Cantrell, because of its terminal position in the alphabet, people said, "and, per se, and," which eventually was changed to "ampersand." (Hmmm. Think about how we slur together "LMNOP" when we say the alphabet. I hope we don't lose any of those letters!) When we want to conserve space, we still substitute the ampersand for the word "and." For sign painters, it can add an interesting flourish and can help with spacing. Long before Twitter limited us to 144 characters in a message, we had telegrams where we paid by the character. In this case, the ampersand's brevity was allowed a place on our keyboard but not when we recited the alphabet.
Another letter that you have seen is the ash, the combination of AE that dates back to Old English. We still see it in churches and in words like aeon (eon) when a writer wants to lend a sense of age or gravity to a piece. The reader has to pause and recalculate the word, which gives the word and the surrounding text more weight. Most word processing programs include the ash under special characters (along with dingbats), so you, too, can integrate it into your writing. It's probably fortunate that it is a little more labor intensive to use the ash than an ordinary "a" or "e." Including it too often would take away some of its grandeur. It's a little like keeping your tiara in your jewelry box for special occasions. If you used it every day (just as if you wore your tiara with your jeans), it would become a joke.
The article goes on to describe nine other characters that have been dropped from our alphabet. I hope you will take time to read about them--and to check out other articles in Mental Floss. Let me know what you think!