It's one of the strongest marketing moves nowdays. Imagine the amount of "secure" messengers out there in which you only have a "word" from the company saying that it's secure. But they deliver a full closed source service in which there is no way to believe or not. So marketing works.
That this has become an area companies are competing in is a good thing. The fact that it was necessary is sad but I don't blame the companies for that. When it is the area for competition it will naturally be the focus for marketing - providing that the marketing matches the reality and isn't misleading that is also a good thing so people can know where the privacy is and choose it.