[LotM Books] Why are the books taking so long to come out?

I've bought the first volume of the physical books a LOOOONG time ago, and since then the second one has come out already. I've read both, and I'm currently waiting for the 3rd to come out, but it's only estimated to come out late May/early June. I know printing and stuff takes time, but the story is already written and formatted, so I don't understand what is taking them so long. It feels like they aren't prioritizing the physical editions at all. They haven't even finished the chapters that were adapted in the donghua. By the time they're done, One Piece will probably have finished or something like that.