Old People Seen but not Heard in Nanjing

Many Chinese cities now allow riders of mass transit to use various rechargeable methods for paying bus, taxi, and subway fares. Riders boarding don't need to fish for small change from the  bottoms of their pockets. They can simply swipe a card across an electronic sensor, which causes the system to emit a loud beep. Students receiving subsidized fares when swiping their cards generate a different response: "xue sheng piao", which is the equivalent of student ticket or student fare. And up until recently riders of a certain age and above generated the response: "lao ren ka" elderly card, or perhaps, senior citizen card.
These were the three responses. Well, there is a response that means, more or less, "please try again" but I don't remember how it sounds. No more than two weeks ago, I started hearing a new response: "nin hao", which is the formal expression for hello used, if at all, by young people to address somebody senior or of higher rank. It sounds like "ning hao" to me, but that's another matter. It took me a few bumpy bus rides with my mind routinely wandering to realize that this new expression had replaced the previously standard "lao ren ka".
I don't know what to make of this development and I've heard nobody comment on it. My first impulse is to suspect that a cohort of the more mature members of society did not enjoy being regularly reminded of their dates of birth relative to the other riders. I know none of them ever complain about the free fares. Is it possible that ageism has become a sensitive topic in the PRC? Is being 'lao' no longer the same as being revered? I don't know what to make of this, but I wish they would stop calling me lao wai and pointing whenever I get on the same bus. A simple ni hao would be readily appreciated.