i know my core songs, but i also use chord cards (about the size of a postcard) with just the chord changes and turn-arounds) and some prompt words...the lyrics system on todays keyboards means all of these can be stored onboard and referred to when needed...so in effect i can have a rep of thousands of songs, rather than the 100 or so learnt by memory and then repeated ad finitum (ad nauseum) for every gig....
reading is a skill, and if not practised is lost...those who refuse to practice their reading would be useless in a session situation or when called upon to back for a solo artist, who DO use charts and god help you if you mess-up!!! nothing pleases me more than getting a new chart book and being able to play it from the "get-go" no practice first, no matter what key,...its certainly a skill i will keep practicing...my early accordion days also gave me the ability to not look at the keys when playing, so even when i am playing bass lines and right hand i can maintain eye contact with the room,with the occasional glance to a card for an unknown song....bottom line its okay for someone to read a chart, as long as they are proficient in physical playing skill and keep some sort of contact with the audience...although when you look at a concert pianist they rarely if ever look at their audience whilst playing, but they still entertain...hmmmmm
cheers
dennis