After the first... ten years or so as a player, I never played very much after that. Basically, after law school about 20 years ago, I stopped playing RPGs as a player (we probably share that in common, I'm guessing), though it's not quite the same thing as I have always continued to be the DM/GM quite regularly over the years.
Funny thing is, recently I started actually
playing in a
Pathfinder campaign. Tournament participation as a player aside, it's the first time I've been
playing regularly in an ongoing campaign in 23 years.
I can admit to the same phenomenon when it comes to me and boardgames, however. I have a very large collection of boardgames - the overwhelming percentage of which I have never played. Mostly, this is not out of choice - I simply have a very hard time finding people to play boardgames with. The guys in my gaming circle are not much for boardgames.
I do think there is one element of "reading/collecting" RPGs where most of us can relate to your experience - and that's
reading RPG adventures.
I can assure you that I have a vast collection of
Dungeon Magazine. I'm missing 3 issues in the entire print series. There are hundreds of other EN Worlders with similar complete collections. And I can also assure you that the overwhelming majority of those adventures have not been played by
any single collector of
Dungeon, ever. No way - no how.
But unlike RPG rule material, I have read that vast majority of those adventures. "Readability" of a
Dungeon adventure was always an important element in distinguishing what made a "good"
Dungeon adventure from a "bad" one. There was more to it than that of course - but readbaility was always an important element.
I have frequently been inspired by a good
Dungeon adventure and often swiped stat blocks or a map here and there. But actually running the
entire adventure? Relatively rare. I'm guessing that's happened maybe 20 times or so, in total.
So reading the adventures for entertainment purposes has
always been an important element in enjoying adventure material in
Dungeon among all or nearly all RPG enthusiasts.
But also, my group plays D&D. I am interested and inspired in all kinds of games. I enjoy reading about games I'll likely never play. i've read Agone, Cthulhu, Og Unearthed, Mousegard, Star Ship Troopers, Buffy and Angel, etc. I've not played any sessions of those.
Experiences similar to this are also
very common amongst gamers. Many groups have a predisposition towards a particular genre and tend to default to D&D in some form as their game of choice. I would guess that a significant number of non- D&D rpg books are read and collected more than they are ever played and used in a game setting as they were intended to be used.