My father was drafted into the US Army in the late 60s and eventually posted to Fort Huachuca. So, when my parents married, their honeymoon consisted of making the trek from Baltimore, Maryland to southeastern Arizona. Along the way, they stopped in a wide variety of places they'd never visited and seen things they'd never seen before, like Maryland Fried Chicken restaurants, something that, ironically, didn't exist in Maryland.
My parents eventually returned to Baltimore several years later -- by way of the Netherlands, where my father was later posted and where I was born -- but my Dad had been bitten by the travel bug and so I spent most summers of my childhood traveling up and down the East Coast, seeing the sights. We weren't just sightseers, though: we usually stayed wherever we were visiting for three or four weeks, which gave us a chance to "live" there as well. My sister and I loved this, because we got the chance to find out what new shops and businesses existed in these far-off states. The two we'll never forget are the grocery store Piggly Wiggly, which we first encountered in North Carolina, and the Christmas Tree Shops, which we first saw in Massachusetts. Like our parents before us, we were struck by how diverse the country was. Sometimes this delighted us and sometimes it amused us, but it never failed to make our long trips fun, because it cemented the feeling of our having gone "away."
I bring this up because, back in the day, that's what gaming used to be like too. Every gaming group was its own little "region" with its own interpretations of the rules and its own little traditions and even rituals. I had a good friend in elementary school who had his own D&D campaign in his neighborhood (we lived some distance apart). Whenever I would sleep over at his house and "visit" his campaign -- something else that used by quite commonplace -- I knew that I was going to play the game according to their rules, not mine. They didn't use critical hit tables, for example, and, while I thought that was odd, I learned to accept it. Similarly, when I went to a game day at the local library -- another telltale sign of just how big gaming used to be -- I understood that I'd play according to the way the referee at my table ran the game, regardless of what I did back home with my friends.
I have to admit that I miss this bygone state of affairs. First, I miss "visiting" other campaigns. Nowadays, I'm lucky that I have a semi-stable group of players at all and I expect that's true of most gamers. I'm sure there are other gaming groups in the city, even ones playing games I like, but I have no interactions with them. Every group seems to be its own little island, cut off from everyone else. You don't get a lot of visitors dropping in for a session or two here and there. Instead, gamers nowadays seem to interact online by arguing with one another on forums rather than actually playing games with one another outside their existing group.
Second, I miss the days when simply playing under another referee was as exciting as the adventure itself. This guy is anal about tracking encumbrance, this guy doesn't allow monks in his game, and this guy has changed the way the magic system works. It really was like visiting another country every time you sat down at someone else's table and, while I'm the first to admit that not every such visit was a pleasant or enjoyable one, so what? As I've said before, there are no guarantees in gaming. Sometimes, even playing with my regular group isn't as fun as I'd like it to be, but that's the nature of the beast and I've come to accept, indeed embrace, it as one of the essential features of this hobby.
I'm not entirely sure how or why things changed, but they did. I suspect that the change maps pretty closely with the end of D&D's faddishness, as more and more people moved on from the hobby and never returned. There are still tons of gamers out there, but there's far less of a web of real life connections between them than there used to be. That makes it harder for them to take their character from one campaign and go and visit someone else's. Likewise, the "tournament mentality" seems more commonplace than it used to be. Again, that's not to deny that gamers make and use house rules -- house rules are in an inescapable part of gaming -- but I suspect individual campaigns don't vary as wildly in this respect as they used to do. Of course, how would I know for sure, since I haven't dropped in on anyone else's existing campaign in years?