@Jarethan
you're not imagining it, and actually there's a fairly clear-cut reason for it, and why it seems different from other cult-favorites that closed early.
It's because of the highly unusual circumstances surrounding its closing:
Beetlejuice was doing well at the box office, and had an avid fan base. It had a nearly-miraculous turnaround after it performed on the Tonys, and was at the height of its popularity - when it had the rug abruptly and unexpectedly pulled out from under them. The negotiations with the Shuberts and Scott Rudin went horribly against their favor, and the Shuberts made the highly unusual decision to retro-actively invoke their stop clause from Beetlejuice's early weeks of under-performing at the box office. And all of this happened because Music Man was such a sure-fire bet to rake in a ton of money for the Shuberts - it's rare that such a sure-fire hit comes along, and even rarer that they demand a specific theatre, and even rarer still that the current occupant of that theatre is still doing very well financially, and yet again, even MORE rare that the current occupant had previously been doing poorly enough to allow the landlord to invoke a stop clause.
And when all of this combined with the show's avid fan-base, I think it's creates a sense of shock, frustration, and also potential hope: most of the time when a cult-hit closes, it's because they were flopping financially, so once it's closed, it's closed, and even the most passionate fans can understand that. But Beetlejuice was doing well enough that they could have POTENTIALLY moved to another theatre and continued playing. It was always a long-shot, but the fact that it was even a possibility is what has inspired the conversation to continue on and on.