I'm all for individualism in most contexts but having been the person responsible for the bulk of an organization's message to its customers (email, social media, and phone call etiquette), it's not a malicious intent here. The only way you can accomplish a consistent message is by rules like these, and the people outside of the organization who are dealing with it want a consistent message.

When you're speaking on behalf of an organization, be it a business or non-profit or government or whatever, you're obligated to use their words. When I pick up a novel I know I'm reading the novelist's ideas, but when I call tech support I'm not looking to talk to Joe or Jane, I'm looking to talk to AT&T about why their DSL equipment in my neighborhood is broken. They aren't personally responsible for it, they're speaking for the company.

This even extends to political press. If you go read the submission guidelines for virtually any news or political publication that accepts freelance inquiries, you'll find that they all suggest reading a lot of their prior articles "to get a feel for our tone and style," if they don't just outright hand you a style guide to read such as the one linked.

You can be you standing in plain clothes on a street corner by yourself. You can't be you when you're answering the company's phone. It's not nefarious mind control, it's just business.