If someone manages to still mess up their phone at that point, then it's on them. It's certainly no reason to allow anti-competitive behavior to go on unabated.
People will always blame the vendor rather than blame themselves. Just one gem of Viral app that is shown to be dangerous
after a couple of million phones have been "infected" would result in virtually flushing a trusted brand name down the toilet.
Don't you think that millions of little Tommy could convince his parents to allow the lock to be turned off to download something that all his friends are playing - yeah alot of parents are that gullible, and yes they should be more hands-on, but millions of parents are that uneducated on tech related stuff save for posting selfies on instagram or chatting on FB.
The same people who were expecting to bask in the inheritance of Nigerian Princes are the very same ones using the internet today, the same ones falling for "Tech Support" scams, and the same ones who will willingly unlock a device to allow malicious software if it looks reasonably legit.
Also, your analysis of kid's and parent's ability with phones is quite a bit off I think. The people with kids now are millennials and some of the youngest gen-Xers. Even the very youngest millenials are 24 now and the oldest are
approaching 40.
The people with kids now all grew up with computers and transitioned to smartphones and tablets without issue. Parents have grown up with this technology, you just hold it in your hand instead of using it at a desk.
Being a child or teen while the internet as we know it now was in its infancy, is not the same thing as making educated decisions. With the sheer volume of applications / games / social media apps at everyones fingertips today it is nothing like the pitiful number of
popular software programs that were available when they were at school/college and being told don't click links in an email.
I used to do computer maintenance for these so-called responsible people, and while savvy enough to unlock, install apps and
use a device proficiently, most are certainly not savvy enough to pay heed to what's nasties they are potentially letting into their devices once they do.
They aren't IT experts, they don't care about the security until their credit card number has been stolen, they don't read malware reports from Norton or Macafee and the only Tech related news items they are going to care about is how many more megawhatsits that the next iPhone includes which they only see because its posted on Facebook (which half of them think
IS the internet).
People
are willing to take a risk of switching off security features if the reward appears higher, and I believe that the opportunity of being rewarded with some awesome viral app, just by hitting that "switch", will be made too attractive for many to avoid.
I'm not saying it is tempting from a Power Users perspective to be able to download apps-from-anywhere. But let's say a viral game like Fortnight was ONLY available by direct download, not available on any app-store. Wouldn't you think that might force the hand of all perspective players to grant access ? Now they know how easy it is, they'll do it again, and again, and again...until boo hoo, my phone was hacked all my contacts got sent that bathroom pic and my bank account is zero. Apple phones are crap.
And then of course there another side of things which the App Store has virtually eliminated - Piracy.
So in short, no, I have zero faith in the majority of "adults" to make informed decisions about whereabouts they can install an application from. I can't fathom for the life of me understand why all schools don't have dedicated social media and internet security education programs by now so we might be up to it in a few years.