Voicemail doesn't seem as "on the record" as email. I wonder, does this matter?
Funny, I had the opposite response. Since it was Coca Cola HQ that ditched VM, I was guessing they didn't want those records around. (Sarbanes-Oxley requires maintaining the VMs IIRC).
As many point out, there's more verbosity to a VM than email/text, and that can work against you in bad situations, like an investigation.