@Alex I’m going to try to give you a serious answer that makes sense. ::crosses fingers for luck:: and has almost nothing to do with THAC0 or OSR, besides recognizing them for the calibrated “buy triggers” that they have become/been created to be.
CAVEAT LECTOR: What follows is a simplified but rambling version of the most pertinent processes. I mean to say, “Yes, Dear Readers, your conflicting anecdotes and preferences can be true at the same time as these principles.
Like Batting averages and The Dow Jones, the concept below should be considered as a view of the aggregate.
When we feel oddball nostalgia for things, the nostalgia isn’t actually about the things themselves so much as the strong positive emotions we felt back then.
Ages 11-24 or so are the golden years of peak emotional intensity in all its adolescent glory without as much of that pesky prefrontal cortex doing its job as a wet blanket and dampening things. During this time we’re all laying down the firmament of our brains’ executive function—“command and control” areas don’t usually finish maturing till around age 25.
(And to make things worse, the biological jobs of maturing can be left in a pretty half-assed state for teens and young adults who regularly use a lot of booze/drugs during this period, all but locking them into a lifetime of challenges with impulse control, though not necessarily about booze/drugs… this is also when process addictions, eating disorders, and sexual fetishes—compulsive behaviors are compulsive behaviors are compulsive behaviors, with or without street pharmaceuticals—start to make themselves apparent…)
So our most emotional chemically brain time also tends to be the same time while our most advanced brainmeats are busy establishing our personal infrastructure of strongly held values, ideas, and beliefs about which behaviors will reliably get which pleasurable or painful consequences the most intensely.
I.E. it’s the time our brains are hardcore building Triggers to like stuff, to seek it out, to repeat the behaviors that make us feel good, and to protect/hoard the good things that we have come to associate with the waves of emotional chemicals. Similarly to dislike, avoid, defeat, or escape from the bad painful annoying stuff.
Hence anything (even THAC0 based D&D!) that gives us a ton of social bonding (oxytocin pinging) and social learning rewards and is new and interesting or meaningful ( endocannabinoid receptor thumping ) and just plain repeatable because it’s good for the human animal or the tribe (dopamine flavored fun)—is highly likely to get subsumed into the emerging sense of “self” and affect our behaviors in much the same way as a car tire’s alignment does.
We’ll keep doing the stuff that reminds us of times we felt really good especially when those memories were laid down earlier or times of high emotion. We’ll also keep avoiding or pushing back from things that remind us of being stressed out, helpless or hurt.
We build nuances into our firmament as we go with new layers. As we experience new big emotions or traumas (or infusions of drug chemistry which the brain can’t tell the difference, apart from how much more dopamine is bebopping around in the brain ) we sometimes create overriding triggers that are more situationally pertinent. Proactively retraining your brain such as with cognitive therapy or meditation practices can take you a long way.
So if I haven’t made your eyes glaze over and start scrolling yet, here’s the big picture answer:
We felt “do that again” flavored brain chemicals at certain times of our life so when we are reminded of those times we feel good again and of course want to “do that again” so we can “feel that again.”.
But there is a tolerance effect after awhile and even though we don’t get the same level of “feel that again” idiot brainmeats keep chasing, trying again and again to get back to that same feeling by encouraging and liking and reminiscing over the trappings of that time.
If it sounds like I’m saying nostalgia (even for THAC0) rides on the same suspension as addiction…yep, just at the more subtle end of the spectrum of our normal natural selection learning processes.
Entertainment, Fashion corporations—religions and politics too—have had this way figured out and using it to make bank/stay in power for a long time. Pretty much every decade, there is some new demographic arriving on the economic scene with triggers ready to be pushed, soon as the marketers figure out which new “buy triggers” to point at which subgroup based on their needs and spending capacity.
Ok enough long rambly posts for me for one day.
I’m feeling nostalgic for my pillow. 
