The "buy a case its cheaper" argument is silly. It was neither the question nor addresses the core issue which is, "Is applecare+ worth it?". Insurance in general is profitable for a reason - it is priced based on probability that it gets used and the cost of replacement. Sure, across a general population it may not be "worth it" as the likelihood you need it may be low.
But this is a very person specific question. For example, if you do not want to use a case, have young kids, etc you may face a much higher risk of a screen crack or some other non-standard warranty issue. If you think the probability is high enough, then its likely worth it as the replacement cost is a little more than half of the out of warranty replacement cost (for a 6+) and if you have two incidents then its only 25% of the total replacement costs for two. Or looked at another way, its ~15/month amortized over 1 year to have it or ~8/month over two years. That is the incremental cost you are paying for to have it.