In today's tech age, apple has replaced/upgraded all Macbook lines and none but the 13-inch still has an optical drive left. Moving forward, this is why i still have my MBP non-Retina from Mid-2012. However what happens when apple starts saying "we have no more parts available?" when it goes in for repair. Even though parts would be available, there would be no indefinite.... Therefore at some point the parts may no longer be available.. In such a case, what would Apple do, tell the customer to upgrade their Mac ? Even though you could find parts if eBay and DIY, that's at your own rusk anyway, and at least if you repair through Apple, you know if will be genuine and reliable. If, and when, such a day comes, you may say "users may upgrade before parts run out", but what if you don't want to upgrade...? Aka it's the only Mac you like using, and while the rest are thinner, your comfortable with what you have.