I don't think I've ever actually encountered a club that forbade singing from the page, but think that they would be well within their rights to do so, if that was their approach to music. It is not as though there was only one club in the land, one place to play/sing, and some overall gauleiter was dominating the land. It isn't that way, and to argue it is can only weaken whatever case is being made.

I go to a club to hear singing and/or music. I believe that the relationship between the performer and the audience, from the highest professional to the most embarassingly amateur, is part of the performance. I don't believe that you do get the same quality of performance if the performer has to consult the words. I do believe it shows arrogance by the performer and is derogatory to the club audience. (I don't need to learn, I can do my practicing here, the audience doesn't matter a **** anyway.)
I thought the whole point was to step up and show something you had learnt, something you could do, not one step in the learning process. Is this the "me, me, I want it NOW" generation in action? Or just everyday selfishness? You want the public acknowledgement of performance, the respect, then you have to learn it and earn it. Not that the ocassional example (whether through age or whatever) is going to destroy traditional music, or any such nonsense, any more than any single poor performance is, but a widespread adoption would.

As for closing your eyes to tell them apart - well, I might if the sound was particularly good, but why should I? The performance is more than just the sound produced.

Art isn't paint-by-numbers. If I want to see people reading I would go to a reading club.

Tonight is a singer's night: I'll see if anyone reads from notes whilst singing/playing.

re the Romans: it is a gross misunderstanding to suggest they were rigidly unchanging. Archeologists can detect different periods in the Empire from the pottery, or from the Army's uniform and equipment, to name but two visible areas. Change was slower in those days than nowadays, but it certainly still existed. If you wish to quote an attempt to freeze society, then perhaps Japan's Samurai culture was one notable attempt.