Thom - a bug is a bug, regardless of how it occurred. Daft example would be 100 of us reporting the same bug, once every two weeks over the year, but without detail of what we were doing - would Xojo bin each one and hence ignore the problem?
But if they were kept - perhaps you might start to see a pattern. And if they were kept your internal KPIs would be more representative of the pain your customers feel. And you might start to see trends in your KPIs that are representative of the improvements (or otherwise) of your software.
I've had the same problem in the telecoms world, where operators try to discount faults due to stuff beyond their control (eg rain fall, storms etc), but the poor customer still feels it, and if their systems were better engineered they wouldn't suffer those problems.
I would hope that some preliminary work is done on all faults reported, regardless of whether or not there is info about the environment that caused it, and that faults are not ignored just because they can't be reproduced.