Well from where i see it, they’re an extension of an existing model, meaning they’re easier and less time consuming to make but at the same time they offer a variation in behaviour, greater livery coverage across one main aircraft type, and so on. For example, I love the fact that you get the old 747 cockpit on the -200, SOFIA and the SCA models, but the more modern displays on the other types - gives you a great feel for how the pilot’s ‘office’ changed over the years and those who like the traditional take on things can enjoy the airplane just as much as ones who like the more modern touch. People have asked for these models as well, so it’s not like they’re randomly added for the sake of it.
Personally, I’d actually go one step further than you, and say that there are far too many modern twin-jets in the app. I wouldn’t remove any that are already added, but I would love for the app to delve deeper into aviation history. Caravelle, 707, Tu-154, Comet, Tristar, Bf-109, iL-2, Super Constellation, Be-200… the plethora of various GA planes that would make great use of the enormous quantity of small airstrips around the maps in IF… - basically there are plenty of opportunities that go unfilled because people just want the A350 or 787 or [insert a tube with wings and two smaller tubes here].