To make more money?
I mean they are already making 3-4 books a year.
Adding 10 extra pages a year could add 50-100% more sales to a book.
Do you know how much a new class that speaks to a new playstyle would sell?
I mean They still printed Strxhaven en after the the initial cool ideas failed and the book became 1 race, 2 feats, a meh adventure, and half done relationship system.
SHOW OF HANDS!
Who here would be a D&D book with a new class and a new subsystem that speaks to a weakly supported playstyle in D&D?
(raises hands)
So ... based on your opinion which is unsupported by any actual data, surveys or feedback from the broader population they could greatly increase sales? Color me not convinced. If there were that much demand for it some 3PP would have stepped in and provided a "Book of Options". 'I mean you could do a survey, not that this site is particularly representative. I've just never seen much demand, make that any demand, for it over the past decade with any of the groups I've played with.