I don't agree with those who say "I'm not a performer, I just want to sing". Any time you lead a song, whether it's on stage in front of an audience or taking your turn in a singaround, you are a performer. You're not simply singing for your own pleasure, you're there to entertain, even if only to a small degree, the people around you. Audiences are generally sympathetic and supportive, but in return you have to make an effort.

Singing is a art, and a craft. There are skills and techniques which need to be learned. Remembering words is one of them. It's a skill which comes with practice, like any other. Unless you suffer from some neurological disorder you should be perfectly capable of remembering vast amounts of information. Unfortunately we live in a culture where we don't need to rely on our memory, because it is so easy to look up information we require in books or online, so our memory gets lazy. We are all capable of much more, it just requires practice and finding a memorising technique which works for you.

I don't have an especially retentive memory, but I am capable of remembering a lot of songs and tunes, including long ballads, because I've practised them. If I'm intending to perform them in public, I rehearse them beforehand, even if that just means singing in the car on the way there.

As for the person who asked if he is expected to practice a song 100 times before performing it in public - why not, if that's what it takes? No one said it should be easy.

Someone said an amateur practices until he gets it right, a professional practices until he can't get it wrong. Amateur or professional, if you're going to inflict your singing on other people in public then you should be prepared to put in the work, the study and the practice to do it to the best of your ability. Why should it be "good enough for folk"?