The following article kind of struck me as being pretty accurate, at least for me.
The first part is a bit longer than it needs to be, I think, but it's sort of interesting how it's not as strong a bond when you replace ultimate with any other sport. Some other activities / hobbies, yes, the story is the same. But not really other sports.
The alter ego thing is also not necessarily ultimate-exclusive. I participate in a few other activities that I only casually mention (like playing Magic the Gathering). And I think that's similar for other folks as well. One lady I used to work with was into ballroom dancing, One person involved in orchestra. I'm sure I "wouldn't get it" and there were significant gaps in the watercooler chats. The occasional physicality of ultimate plays a role, though. I've had more than one Monday with an "interesting walk" due to either soreness or an ankle issue.
Before I make this email longer than the article itself, I'll close by mentioning that daylight is quickly fading. We're ending earlier and earlier on weekdays, so take advantage of it while we still can. Although we will likely be going until daylight saving time ends (first week of November, I believe), sunset on Nov. 1st is at 5:44 PM. And it's sometimes cold (but sometimes not). So I'd advising packing a broad set of clothes to wear / change into.
See you on the field,