Missing the point. Sure, many users will trust the Netflix app, but we only need one trustworthy app (like Netflix) to open the gate for all other kinds of untrustworthy apps to also skip the check.
Now you're in the situation "I've already done this, nothing happened. But of course, I shouldn't do it all the time. There's a reason the warning is there."
Now you want to try out this other app. The company doesn't seem shady, but they're new, they don't yet have the reputation Netflix has. So you don't trust it "absolutely", but "pretty much". OK, you go ahead, just for this one app.
Now you're even more used to clicking through the warning. Repeat a few times. Now you're installing totally_not_malware.apk. What could go wrong? You've already installed a bunch of apps this way with no issue. Plus this one app clearly isn't malware, it says so in the title! Also, all your friends are using it and you don't want to be left out.
Android has only been asking once per source, not per app, for a while. Also, the messages aren't that scary. Folks haphazardly click OK in Windows without reading messages; you can be sure they do the same on a phone.
Most people I've heard referred as "tech savvy" are just plain old gamers, and they can be easily tricked.
The App Store (and reduced API surface) was a true revolution for the customer. Remember every app installer requiring admin privilege on Windows and creating it's service that runs at startup checking for updates, littering the registry and sometimes installing drivers?
All gone from the App Store. If the app maker doesn't like it he can go target another platform.
Even on Android, the amount of useless software side loaded by the manufacturer is mind boggling.