Apple started removing apps that have yet to be updated for "a significant amount of time" after 30 days. Unsurprisingly, this has angered indie app developers.
Apple’s App Store Improvements page shows the company is implementing an ongoing process of evaluating apps, removing apps that don’t follow current review guidelines.
Apple may be tightening down on programs that haven't received any upgrades in a long time. Apple tells impacted developers in an email titled "App Improvement Notice"