How many times I heard that when I was growing up. I was never quite sure why we were expected to respect our elders. I knew it was probably something to do with wisdom of age, and possibly because they had done stuff from which we benefited in some way and for which we should be grateful.
Now that I am elderly I can see some arguments for demanding respect, at least for some of us.
You know you are old when you become aware that the pains are not only there to stay, they will continue to increase in intensity and location. You learn to live with them because there is only one alternative and you are working hard to delay that one. If you are not, you should be.
Contrary to what some people seem to believe, complaining about things does not make them easier to bear, and it certainly does not make the complainer easy to bear. While you might feel sympathetic at first, this particular emotion can quickly be worn thin. Just as the joints and cartilage between them wears thin and causes the pain.
I have mentioned my mother in law a few times in blogs; one of the things I did admire about her was how little she complained about the pain she must surely have been experiencing. She had both knees replaced. We know that, while artificial joints help considerably, this is more to do with the ability to move rather than the removal of the pain. I am sure Mildred was in almost continuous pain but she almost never complained about it. Strangely, she found a lot of other less serious things to complain about; perhaps that was her secret, distraction.
So, respect your elders, at least those who don't complain about their aches and pains, because I guarantee you, they are in some degree of pain - continuously. Respect them for not whining about it.