That's because LO is compatible;
opening a document in LO is handled differently from
copying/pasting.
If you're looking for a reason for this;
well, some of these folks on this list should be able to help
you -
sorry, I'm not one of these gurus
In fact, my most recent computer problem arose a few months ago -
when sending out a newsletter,
I do not attach anything although I do often include URLs ...
how some of these URLs appear as attachments to the receiver has
me stumped.