One correction to some comments here: an iOS app cannot list all apps that are installed. You can only check for specific apps/schemes (LSApplicationQueriesSchemes) by specifying apps you are looking to query for installation status or open. You cannot provide a large list of unrelated applications since Apple rejects that during app review.
Apple added these restrictions because installed app lists can be used for fingerprinting and privacy invasive profiling.
Apple added these restrictions because installed app lists can be used for fingerprinting and privacy invasive profiling.