Very often, apps are rejected because they do not comply with Google and Apple policies and rules. Each of the marketplaces has its own set of legal requirements for the publisher, in particular:

Apple requires the developer to provide a link to its privacy policy, describing what information is collected from users and how it is used. Also, the publisher is obliged to collect users’ consent to data processing, to minimize the amount of data collected, and to give an opportunity to withdraw their consent to data processing.

For regulated activities (online casinos, cannabis sales and so on), Apple requires that the app be published from a company with the appropriate licenses.

There are stricter rules for apps that are targeted at minors, apps that collect location data or user health data.

The rules prohibit copying content from other applications or otherwise violating the intellectual property rights of third parties.

The requirements are the same for the Google Play Market.