I truly do not understand why people get so upset about stage-dooring. It seems like some people are acting like it's just people randomly standing outside the theaters, but nowadays most theaters literally prepare barricades and arrange for it beforehand. Actors can choose whether or not they want to stage door or not. The actors themselves comes to the barricades/people. If they don't want to, and they simply want to go home, then they'll walk past or go out a different exit. Literally no one is defending people who follow people home, or ask for someone's entire schedule, but stage dooring in itself seems like a pretty non-evasive thing. No one is forced to do anything.
And while it's not *officially* part of the theater experience when you buy a ticket, it is most definitely part of theater culture now, especially for younger theater-goers. Not sure if that's a great thing, but I also don't think it's a terrible thing either. I don't stage door "obsessively" like some, but I've seen the Cursed Child quite a few times now, and I love stagedooring for that show. I think it's a perfect example of how good of an experience stage dooring can be when done properly. The barricades are long so there is no pushing. There are members of the cast who do not come out, and people respect that. People pay the same respect to the ensemble as they do principle cast. It's pretty well-known that they only stage door after part 2 and people respect that (i.e. i know many people who have spotted one of the cast - even some who don't stage door - around the theater at other times and they won't bother them). Plus, it's cool to talk to the actors about their characters - especially this cast, because they essentially helped workshop/create these characters.
Sadly I know that not every show is like that. I stagedoored for Lifespan of a Fact a weeks ago and it was the most horrid experience of my life. Everyone was there for Daniel, and he actually ended up leaving halfway through because of how disrespectful people were being.
But my point is - you can't lump everything together. (I also would like to add about the numerous restaurant comparisons people keep trying to make - that is clearly not the same at all lol. Otherwise things like Flea wouldn't exist, or they wouldn't be able to sell 100$ signed playbills, etc.. If you think it's okay to exploit people's admiration for cash (which I am not arguing that it isn't okay), then I don't see how you can have a problem with some actors allowing fans the opportunity for free either. Again, it's their choice, they don't have to come out and stage door. That said, in nicer restaurants, it actually isn't unheard of for the chef to come over to a table as a treat, or wanting to give compliments to someone who cooked a meal that exceeded expectations.
At the end of the day, it's personal preference for everyone, but I don't think anyone has the right to be as harsh as some people were being for stagedooring alone. Stalking is obviously a whole different thing.
now to actually answer the question of the thread...
I think a small thing that might add to the issue is who exactly is being cast. A lot of shows will cast a big name - sometimes a name moreso linked with hollywood than broadway - and this brings in people who only want to come for that name. Re: Daniel Radcliffe being cast in Lifespan of a Fact (which he's brilliant in). So many people were coming to stagedoor who didn't even see the play that there now exists two separate barricades; one for people who saw the play and one for people who didn't.
And there's obviously a huge handful of others. Sometimes even if it is a solely-broadway person, but their reach has expanded to "fandom" levels (Like the cast of DEH).