One of my biggest gripes with using old iPhones and iPads as offline media devices is that Apple is extremely stingy with storage space so most likely these old phones only have 16/32GB of storage, making them a pain in the ass to curate a media library in them.
If only they had expandable storage. But they don't even support mounting SD cards directly from an external adapter, you have to import the media in bulk, making them useless.
These security measures don't actually deter the theft itself. The opportunity cost is simply too big, even if only one in 5 people are intimidated enough by the threats to unlock their phone, that still makes it worthwhile to steal iPhones.