1. Insert install disc/USB.
2. Boot to install disc.
3. Spam the next button.
Installing new Android OS versions manually often involves custom third party unlock tools from sketchy download sites.
I worked in a Computer Repair shop for years through college and believe me, the average user has ZERO interest in installing or re-installing an OS. They will pay >$100 to have someone "spam next a few times" as you put it.
I would call that a distinction without a difference. End result is the same: non-technical users do not do it.