How old is the "older" person? 30? 60? 90? In the last case, respecting a 90-years old person is usually not about appeasing power.

It seems more like retirement insurance. A social contract that while you are young, you have to respect old people, so that while you are old, you will get respect from young people. Depends on what specifically "respecting old people" means in given culture. If you have to obey them in their irrational decisions, that's harmful. But if it just means speaking politely to them and providing them hundred trivial advantages, I would say it is good in most situations.

Specifically, I am from Eastern Europe, where there is a cultural norm of letting old people sit in the mass transit. As in: you see an old person near you, there are no free places to sit, so you automatically stand up and offer the old person to sit down. The same for pregnant women. (There are some seats with a sign that requires you to do this, but the cultural norm is that you do it everywhere.) -- I consider this norm good, because for some people the difference in utility between standing and sitting is greater than for average people. (And of course, if you have a broken leg or something, that's an obvious exception.) So it was rather shocking for me to hear about cultures where this norm does not exist. Unfortunately, even in my country in recent decades this norm (and the politeness is general) is decreasing.