I don't know why that has to be, but it seems to be the case. I've taken my MacBook Pro into the Mac Store twice for dvd/cd drive repair, and each time the internal drive was just replaced - no inspection, no cleaning; it wasn't worth it.
Now that my Apple Care plan has expired, and my internal drive is on the blink again, I'm looking for an external drive, thanks mostly to reading that recommended here. I've found this one at the link below, and amazon is great about taking things back if they don't work as advertised, and this one has free shipping to you and back to them if you need to return it:
http://www.amazon.com/gp/product/B001P5C9S0/ref=ord_cart_shr?ie=UTF8&m=ATVPDKIKX0DER
The same item is for sale online at the Mac Store U.S.
I thought I'd try cleaning the drive first, as that was suggested to me by a salesman at the Mac Store, but the drive won't accept the cleaner disc!
I have an older mbp and the same thing with mine. I just spray compressed air into the drive port with the extendo stick and it usually works for a while. at least then it'll accept the cleaner disc and i'm good to go for a while.