There's always a need, example I could not stand the bad aliasing up to the ps4 era, therefore I will quickly update or repurchase games on the newer consoles just to have a sharper cleaner picture, why wouldn't I? That's like someone having an iphone 4 and never ever upgrading it. Why would I limit myself. Some repurchases are actually very cheap, GTA5 was like 10 dollars for the full game and looks miles better than on the ps3. Another example, shadow of colossus, just try playing it now on a 75inch screen on a ps2, it will look totally horrible compared to the ps4 remake. I would never even think twice about getting the upgraded version. Games are not movies or music, video game graphics actually improve very quickly in just a few years. I cant even manage to play ps3 let alone going even further back. I tried the first infamous on ps3 recently and I just couldn't do it, and even tough all ps3 games are free, I still don't want it.

Financially inflation hasn't hit my pockets yet, but I am a higher income earner.
I can still rush out and buy whatever I want.

But on the flipside there hasn't been any recent game releases that have interested me.

As I said, I'm one of those people who like to play games the way they were originally released. I own a CRT, so all the pre-HD games look really nice and sharp (as well as suffering from no input-lag), which takes care of the issues you're describing having to do with playing old games on new TVs. And then there's things like aesthetics, nostalgia and sensory etc. There's nothing quite like playing an NES game on an actual NES--especially if you're from that era, like me. Same with all the old consoles. If you really want to time travel for a few hours, there's no better way than turning off the lights, sitting down by yourself late at night and popping Silent Hill into your actual Playstation on a CRT while holding a real Dual Shock 1 in your hands. Takes you right back. 

The last game I bought for the multiple time was Mario 64 when I bought the Super Mario 3D All Stars. I'll probably resist buying The Last of Us part 1 remake and wait a year or so for it to hit Playstation plus extra.

I don't double dip unless I can get one or both games at a decent discount I never spend full retail price for the same game twice.

I don't think I ever properly double dipped.
I have bought twice by mistake, and have bought for remaster/remake. But otherwise I won't buy for different system at the same time.

Besides using the different strokes for different folks analogy for why some people do what they do, the only other reason that I can think of is if your a collector who buys and keeps the Collectors/ Limited Editions untouched and then buys the standard game to play.

Inflation or not, why would you buy multiple copies of the same game? Waste of money. Just buy one copy, play the crap out of it and move on the next game. Too many games in the world to just keep grinding the same one over and over.

I never did.

Surprised no one mentioned they double dipped on a digital version for a couple of bucks for convenience when they already own a physical version.