In a ploy to keep people paying for apps, Apple will let developers offer discounted subscriptions to current and recent subscribers. Until now, developers could only offer freebies and introductory discounts to new users, which means that they couldn’t easily incentivize lapsed subscribers to re-join. As more apps turn to subscription models over one-time purchases, this change will likely go over well with developers and users alike.
Apple opens in-app subscription discounts to existing users
To retain subscribers, developers can offer discounts to both new and existing app users.
Source: https://www.engadget.com/2019/02/25/apple-in-app-subscriber-discounts/