Were they shipped to various locations, including across major oceans? How many times? For example, my personal anecdotal experience receiving items from Australia, and even the UK, is basically the flip of a coin. I never buy disks from the UK or Australia anymore. I'm in the USA, and I think something about that travel just ruins things for some reason. Or, all those folks are shady!
I assume some reasons that software "suffers" from those long trips are:
1) Vibration/Shock - I can imagine that some packages/boxes are handled quite roughly
2) If it is crossing international borders it will go through customs - I assume electromagnetic scanners are commonly used at customs. Can imagine that those can potentially be quite bad for disks.