....Your story sounds like selection bias.
Unfortunately, no; it's not. I have an incredible memory (with the exception of names). I can recall experiences in vivid detail from decades ago. Not even joking. Was legit shocked the first time I realized that most individuals completely lack that ability. Nothing selective at all.
Very last time I helped out a stranger who expressed genuine thanks was two decades ago. I was in a dinner situated between Macy's on 34th street in Manhattan, and Madison Square Garden further up. A young man came in with a few of his friends. Mixed group of guys and girls. Place was near empty. They sat two tables away, directly to my right. The young man actually said "Excuse me," then proceeded to ask for the time (clearly having noticed my wrist-watch). I told him, and the "Thank You" that came out of his mouth was genuine. THAT was the very last time.
But perhaps we are counting, politeness based on what certain people don't do when sharing spaces open to the Public? Fair enough, bit earlier than two decades ago.... There's a White Castle in West Hempstead Long Island that my friends and I used to frequent. Oh! I could tell you some fascinating horror stories of that place! But, I doubt you want to read a novel. Short version: People who worked there? Ghetto trash mentality. To be clear NOTHING to do with race. The people who ate there? Same thing. Oh, and the occasional random druggie lunatic. (Like the elderly one who challenged me and my two friends to a game of Midnight basketball in the mostly empty White Castle parking lot one night. No, there is no basketball hoop out there.)
But I digress.... A pimp with three of his "Working Girls" came in one night. They didn't yell, they didn't shout. No one was shaking because they needed a fix. They weren't in there propositioning my good friend John.... Nor any other dudes who happen to be named "John." (Yes, John is his actual name.) They ordered their food, sat down at an out-of-the-way table. Quietly ate. Didn't bother anyone. Didn't disturb anyone. Based on how all of them were dressed, everyone in the place knew.
Think about it.... The most respectable, and most respectful people in that place were a pimp and his girls! I drove all the time back then. After an incident with a polite but threatening racist stoner who sat uninvited at our table, while his two non-stoner friends watched; apparently happy to let three dudes pound the crap out of their rude friend who was as high as the stars up in space.... I put my foot down! No more hanging out at that piece of trash White Castle just because it was the only one in the area! And no, we didn't pound the racist. My friend Dan defused the situation while I sat there with one of my self-defense tools that I palmed under the table just in case things got out of hand. Danny always was a charmer. Not always a good friend though.
All true. If anyone doesn't believe me, go ask my friend Dan.... He's currently the Director of Sports betting at the New Hampshire Lottery. Mister
I'm never leaving Las Vegas! (Guess they offered him enough money to move back to the East coast. He must be bored out of his skull.)
Edit:
Typo.