Companies commission a brand voice, receive a document, and find within a year that their communications sound like whoever wrote them. Consistency is a maintenance problem.
Voice is produced by many people
Customer-facing text is written by support agents, salespeople, product designers, marketers and contractors. Most never see the guidelines and none were hired to write.
Each writes in their own register by default. The aggregate is a company that sounds different depending on which door the customer entered through.
Which means voice is not owned by marketing in any practical sense, even where the document was produced there.
Abstract guidelines do not transfer
Guidance framed as adjectives, such as confident or approachable, cannot be applied. Two writers will produce different text from the same instruction and both will believe they complied.
What transfers is examples: this phrasing, not that one, for this situation. Paired samples are usable by someone with no training in the way a description is not.
Guidelines that specify decisions people actually face, such as how to apologize or how to explain a limitation, get used. General principles do not.
Review is where consistency is enforced
Consistency requires someone reading text before it ships and correcting it. That is ongoing labor, and it is the item cut first when the team is busy.
Drift is gradual. No single piece is far from the standard, and the cumulative distance over a year is substantial with no point at which anyone chose it.
Periodic audits across channels catch this by comparing text that was never seen side by side, which is the only way the drift becomes visible.
Scale and localization strain it further
As a company adds channels, languages and markets, the number of people producing text grows faster than any review capacity.
Translation is a particular difficulty, since tone does not carry across languages directly. A phrasing that reads as warm in one language reads as insincere in another.
Companies that succeed here define what the voice means functionally, so a translator can reproduce the intent rather than the wording.
The payoff is recognition, not elegance
A consistent voice lets a customer identify the sender before seeing the name. That recognition is what the maintenance cost is buying.
It also reduces friction internally, because writers spend less time deciding how something should sound and more time deciding what it should say.
Companies that treat voice as a completed project rather than a standing cost get the document and not the recognition, which is the expensive half.