Apple restricts how long an iOS app can stay, and what it can do, in the background.
If you wonder why Apple puts such restrictions in place, the Android ecosystem in China is the perfect counterexample. Android phones manufactured and sold in China do not incorporate Google Services Framework, nor is the Play Store available in mainland China. Instead, those phones run on tailored Android OSes. Manufacturers retain numerous backdoors for certain third-party apps, which are often pre-installed. Many third-party apps stores exist, with no app screening, no oversight, no developer policies, nothing.
Among the worst of Chinese apps is WeChat, a social media app that regularly consumes 4+ GB RAM on a phone with 12 GB of RAM, even when it’s in the background. No one knows what WeChat is doing with so many resources.
Another notorious offender, Pinduoduo (brand name Temu outside of China), sends barrages of ads for low-cost goods and sale events through notifications which cannot be turned off. Pinduoduo was even caught last year to have exploited 0-day security breaches, so they can surveil users of the Google Play version of the app. Pinduoduo, one of the most popular online shopping platform in China, was subsequently banned from Google Play in March 2023 for being a malware outright.
Both of these absurd stories involve rogue background activities. Of course, they should never have happened at all. Apparently, Apple feels the only way to fend off such abusers is to put hard limits on background activities, for anything other than first-party services.