Age will do that to you.
Speaking of forgetting lyrics, I got ruined on Fleetwood Mac when I went to see them on their reunion tour. We had kind of a bird's eye view of the stage and we could see that Stevie Nicks was singing off a teleprompter.
She helped to write the songs. She'd been singing them for 30 years. 12000 people in the audience can remember the words, but she can't. I haven't listened to Fleetwood Mac since.