Jack, you seem to be making a couple of assumptions:

1. That singers who use books all want to learn songs but don't know how.
2. That no one here is trying to help those who do want to get rid of their books.

This is wrong on both counts. There are a number of singers who simply say, "I can't learn words, it's too difficult," and would rather not perform than attempt give up their word-sheets. And some are just plain lazy.

If they want support, there are various workshops etc available for singers, some of which will discuss the learning of words. And in less formal settings, it's quite common for the more experienced and confident singers (such as some of us here)to give tips and ideas on how to learn to do without crib-sheets, as well as other issues like nerves.

Making it clear that song-books are not welcomed in a club isn't "door-slamming" - it may actually encourage singers to make the effort to learn their songs, and does not preclude offering support and advice for those who want to improve. It's not that different, as someone up there remarked, from expecting guitarists to have their instrument in tune - that, too, takes a bit of effort and skill.

Marje