Quite a few years ago there was a brief question in one of the daily papers concerning 'train spotters', with a rather interesting answer and comment by a psychologist.
Hea reasoned that there was a deep-seated gene in some people who were able to notice pattersn in things, and to make sense of them. Many centuries ago, when we lived in mud-huts, ate berries, and 'high-tech' was a pointy stick, those people who watched things moving and made notes were one of the most important people in the tribe.
They were the ones who noticed that animals went to watering-holes at certain times of the day, and what time of day there were most (and, therefore, best time to hunt them for dinner). They were the ones who noticed that bright shiny thing going behind the hill every day, and noticed that every day it went a little further north, and the days were hot; and then it went so far and then went back the other way, and it got cold. They knew when certain animals would pass through on their migration, and which animals were easiest to catch. They knew which plants grew at which time of year, and which plants attracted which animals, and which of those were the 'tastiest'.
In essence, these people were one of the most important members of the tribe.
The psychologist likened the 'xxxxxxx-spotters' to those tribesmen of centuries ago, just with a slightly different 'thing' to notice and record. If it applies to train-spotters, then it applies equally to plane-spotters.
Personally, I think the psycho was smoking something. Or maybe he played golf?