I don't know why this is news. Most consumer Android phones, Google's included, require you to acknowledge a warning before the ability to sideload is enabled. Their stance has always been "at your own risk, we don't recommend it" and we always just laugh and say "okay, whatever dude" before we do it anyways.
we always just laugh and say "okay, whatever dude" before we do it anyways.
The thing is for people who aren't used to modding and you try to side-load a random cool app on their phone (or somehow they end up doing it themselves) they might be frightened and may even cancel the installation.
A family member always downloaded and installed APKs from the internet and didn't know about the Play Store cause that is how you did things on Windows.
The person is question has low tech literacy, and they were doing this for years
Yup. Some people try out Linux (and to some extent MacOS, although their app store is a lot less all-encompassing) and attempt to do the same thing, finding random executables online that may or may not cause issues and may or may not even be from the actual developer themselves.
The ubiquity of Windows means that MS's software decisions - good or bad - have knock on effects to other software, such as people doing as you say to find apps, as well as things like ignoring security prompts because of how poorly they implemented Window's User Account Control dialogues.
It's not always a bad thing, sometimes it can act as a positive pressure to improve - e.g. Window tiling/snapping becoming a much more widespread feature after Win7 included it. But man it really can be a bad thing sometimes.