yup,just even the word "sideloading" seems like its been custom created to sound shifty and sidewise when all it means is installing something. People would look at you weirdly if told them "sideloading" Photoshop on to your PC was dangerous, but somehow its accepted for phones.

There may be a little bit of vendor lock in here, but it definitely is also about security. A lot of people are completely oblivious when it comes to tech. Sideloading is easy and there are tons of guides for it, so if someone is tech illiterate they can just follow the guide and install malware ridden apps easily.