Cursed Child isn't really a show that, like Hamilton, BOM, or DEH had at the outset, where it didn't even really matter if you had no idea what the show is about or if you even think you might it, but you just wanted to have the bragging rights to say you saw it before your neighbors. (As someone who worked selling tickets, I had fond memories to trying to keep folks from taking their 6 year-old to BOM back in the day.)
Yes it's a popular show, but 6 hours worth of bragging rights, not to mention using up two nights or a whole day of a NYC trip, that is an exhausting prospect,. Plus, HP already had competition from the existing London production, not to mention the theme parks, there are plenty of other ways to get your Potter fix.
"Hey little girls, look at all the men in shiny shirts and no wives!" - Jackie Hoffman, Xanadu, 19 Feb 2008