expensive drives that wear out or can mangle the tape
This is my main problem with removable magnetic media. The simple act of reading the data actually degrades the storage medium. And if you have a bad drive, it can actively destroy any disk/tape you put in there. And it's actually hard to diagnose if the problem is with the disk or the drive, so you're likely to destroy a few disks/tapes before you figure it out. I've had floppy drives, zip drives and tape drives that have all ruined the storage media. At least with optical drives, it's very unlikely that the disc will be destroyed by attempting to read it.
"If you want to know what happens to you when you die, go look at some dead stuff." -- Dave Enyeart