The Playgoer: Spidey, Your Time is Up:
Yes, there are good reasons we consider a preview process sacred. But let's not romanticize and mythologize it out of proportion. I'm still trying to research when exactly preview performances on Broadway even started, but I believe it wasn't until the 1960s. (If anyone knows for sure, feel free to fill us in.) Before that, opening night was...well, truly an opening night. The way most theatre folk experience it from High Schools to community theatre to most places south of 14th street. Instead, Broadway shows might have a series of "invited" dress rehearsals, amounting to private previews, which were also, by the way, free previews. The big change in the 60s was to actually sell tickets to shows that hadn't opened. But that's why "reduced-price previews" were the norm till sometime in the last ten or twenty years. I guess that was when Broadway producers realized most audiences (especially the increasing tourist portion of the audience) didn't know the difference any more.