Doing an out-of-town on a musical that nobody expects to be an endless runner like Hamilton may be financially counterproductive at this point. The way the industry works these days, you've gotta get four quarters to have a viable show: a Broadway or major Off-Broadway run; a cast recording; a pickup from a major licensing company; and a major production or tour post-Broadway.
If the show does an out-of-town, and it's not great, and reviews are middling, that likely scuttles most of those four quarters from ever coming to fruition unless they pump tons of money into it. On the other hand, if they open cold in NYC, even if reviews aren't great, the title and the composer's reputation will still get it tons of press, probably a cast recording, and that licensing pickup. At that point, money trickles in from regionals and amateurs, as opposed to no money coming in at all if it folds out of town.
Is it a creatively rewarding business model? No, but it's about the only financially viable reason for pushing musicals that nobody expects to change the world and reshape the culture to NYC.