I mean, exactly how invasive are default operating systems? (Like Windows, Mac, Chrome OS, Android, iOS) Do they log your keystrokes, log passwords, capture screen, upload your photos, videos, or audio? (Assuming you aren't a target of government) Is it even possible for the average person who doesn't feel comfortable messing with installing operating systems to have any privacy?
This is a highly loaded question.
You are making a number of very poor assumptions based on a number of ridiculous misconceptions.
The average, everyday, human adult is fully capable of understanding their own personal "threat landscape". How they deal with that will vary.
For most; if not all, average consumers; their concerns are still very limited. They're not so much concerned with the provenance, the history, of companies...they just want to duck for the oncoming threats in their landscape. These metaphorical tree branches are what they're ducking under. They have no logical need to fear the entire tree.
Personally, I choose not to live like Stallman, nor do I have fears of big state repercussions like Snowden does. Neither does your average consumer. Functionality is the top priority. Functionality on-par with the CSSC (Closed-Source Software, Corporate) competitor is critical. If the FLOSS (Free/Libre Open Source Software) version can do exactly what people typically want and expect it to do AND cost less monetarily AND can impact their privacy way less than using the CSSC competitor would, then it will be adopted by many and loved by all who use it.
This isn't to say that privacy does not matter.
It simply means that privacy is a spectrum; and everyone has varying privacy wants and needs. For some reason, a large potion of the "tech-savvy" people in the FLOSS community feel the need to measure their superiority in "How private their systems are." The average user does not give a damn about that dick measuring contest; and really would rather not be bothered. They just want the amount of privacy that is right for them, and their specific situation.
It is best to put your ego aside when discussing privacy, or helping someone else to discover and improve their own privacy.