Every rocker with a hit song with high notes has to change the song in order to still sing it in concert. Layla, Take on Me, Dream On, Don’t Stop Believin’, etc.
If you watch reaction videos from vocal coaches hearing singers for the first time, you will find that they get nervous about the ways singers are tackling parts of their songs, because there are ways to sing that you can do for twenty years, and ways that you can do it that are good for six. Less if you start doing full concerts instead of bar sets or opening act work.
I don't think Steve Perry ever pitched down his vocals. IMO there are two types of singer, ones with good technique (due to practice or genetics) who can sing easily, and those who have to really force notes out in the studio (relying on perfect conditions) then pitch down live.
I agree he always seemed to me comfortable in that range, on talk shows, etc. The guy from Aerosmith on the other hand I would be surprised if he could match the radio version regularly in concert. As for Layla, I guess I only know the live/mtv unplugged and the original had higher notes?
In 1982 the Secretary of the Interior, James Watts, announced that Wayne Newton would perform at the National Mall on Independence Day, at least implying that the Beach Boys, who had been there the year before, really didn't reflect good American values. He was mocked for his, and the next year the Beach Boys came back. I did not go to the Mall, but heard some of their performance on the radio. They were terrible, and a musician I knew said that this was because men's voices deepen with age but the Beach Boys were still trying to sing in the original keys.
I believe it's a joint effect of muscle atrophy (vocal folds lose mass and become thinner), lower testosterone levels, stiffening of the larynx and the general loss of elasticity (stiffer things vibrate with a higher frequency). I'm no expert, though.
To be clear, we're talking about 60+. Before that, the pitch usually is on a decline.
If you watch reaction videos from vocal coaches hearing singers for the first time, you will find that they get nervous about the ways singers are tackling parts of their songs, because there are ways to sing that you can do for twenty years, and ways that you can do it that are good for six. Less if you start doing full concerts instead of bar sets or opening act work.