The show runners for The Expanse claimed that they ended the show where they did because the show had reached a natural conclusion, the books took a giant time leap, and they felt the rest of the story would be better developed into a sequel series at a later time.
Honestly, I think they did the right thing. The TV show was great for what it was, but the last book was just so different than the rest of the series, I don't think it really matters that they left it out.
End the show on a high note instead of possibly spoiling it.
I really hope they work out a way to do a time jump series later on with the same actors who are all actually older (though logistically speaking it would be difficult)
I loved the expanse, maybe more than books. But even the books just got drawn out and I lost interest. With how closely the show followed the books I'm worried the show would just fall off for me like the books.