Further, that's shotgun value. With Netflix, they can show my retired parents a completely different ad on the exact same show than they will show me or my wife - so instead of paying, (using your numbers) $0.032 per viewer with the expectation that about half of them will be misfires (or $0.064 per minute of hits from the advertiser's side - this number is carefully crafted by hand from whole cloth), they can narrow their focus and charge closer to $0.0544 per minute with the expectation that they will be paying for maybe only 15% misfire (same value to advertiser of $0.064 per minute, but more income per ad for Netflix).
And that doesn't even start scratching the surface of the value of a well targeted ad to the right audience - I get a few hundred dollars in swag a year from companies trying to bribe me to listen to their sales pitches. If the right company can get commercials that hit me and people like me, it's really easy to pivot money for sporting event tickets and iWatches into a few dollars per ad. I'm guessing there isn't a company that is willing to pay a few dollars each time they get in front of the correct person, but it only takes a few IT Directors/Purchasing Managers/CEOs to vastly change the math on how much advertisements are worth to Netflix. Suddenly we aren't talking about 13 minutes per day, we may only be talking about a few minutes per day. Maybe two ads when you open Netflix - one from an outside company, then one about the new releases on Netflix you may not know about. Then maybe one when you switch from one program to another. Or an interstitial ad every third time it moves onto the next episode. Sparse enough to keep you from ending your account, and short enough that you don't just wander away from the TV when it starts playing an ad.
The counter-point would be that many subscriptions are less used than others, and the underused ones subsidize the more thoroughly used ones (like gym memberships). My family racks up a few hours per day of use, while my parents may only do a couple hours per week (they have cable TV that they use more often). Converting my family to ad supported might improve the bottom line, but my parents subscription would stop being as valuable to them.
Of course that ignores the fact that I will go back to visiting our good friends in Sweden for my media before I pay to watch ads again, but that's only tangentially the point.