Free trial for App Store apps and games are coming
New App Store guidelines are finally going to allow developers to offer free iOS app trials for all titles, not just those based on subscriptions. Yes, this means you’re finally going to be able to try apps and games before you buy.
According to section 3.1.1 of the new guidelines, to enable trials, developers must create a free in-app purchase with a definite expiration date.
全文及来源：
http://www.idownloadblog.com/2018/06/06/free-ios-app-trials/
Developer
App Store Review Guidelines：
https://developer.apple.com/app-store/review/guidelines/
若开放试用APP，就能让减少使用者被退款搞疯的麻烦，
但要到普及的程度，还需要很长的时间才有可能，
减少买到不适合的APP、不小心就订阅的机率能让使用者轻松许多。