How long do the sound waves from speech persist in a gaseous medium, or the often equally gaseous white matter between your ears? How long does an email, backed up and archived by sender, recipient, archiving software, compliance department, etc, etc persist.

People tend to actually think before they write something down that will last forever. Much less so when they're flapping their gums in real-time. High quality, premeditated communication trumps low-quality, off-the-cuff communication, for me, anyway.