The point is that a ukulele club is a social situation where the rules you're advocating would be destructively inappropriate. As they would be in a church.

There is a downside to memorizing repertoire. It takes time and effort. Which means you're going to want to amortize that over many performances. And if you're always going to be playing to the same few people, as would be the case with a regular at a village folk club, that means they're going to get bored with you. And they're going get even more fed up once they realize your repertoire is shrinking with age.

Schools used to teach relevant skills for performance off a script - my primary school English classes regularly included recitation. I wasn't all that good at it at the time, but I did learn there was a skill to reading words off a page, conveying their meaning and bringing them to life. Playing an instrument or singing from a score or songbook involve similar mental steps.