Unless you have some medical problem, such as short-term memory loss, there is absolutely no reason why people cannot remember lyrics. It all depends on how much time you are willing to invest in memorising them. Failure to memorise the lyrics is, in my opinion down to laziness. I have no wish to offend anyone, and I haven't got the greatest memory in the world,(ask my wife)but I know the words to at least a few hundred songs, of all types, and I don't carry a folder around with me to gigs. On the odd occasion my memory lets me down, I sweat buckets, just like everybody else. :)