User blog comment:Anylist Amethyst/The REAL Reason Old Recurring Characters Aren't in Season 4/@comment-4801337-20180206190436

It's usually mostly because of the actor contracts and their availability. Mack and Madison appeared only once in season 3 and haven't been a big part of the show lately.

Lincoln (Mack) and Molly (Brianna) can do both Disney and Nick. Sofia can't do both because she's a lead on Andi Mack. So, we probably won't see June again.

Natlee is the most noticeable one missing but that's because Siena was filming her new show. I think she will still be back towards the end.