It's what I conclude after noticing that few brands have the guts to say "we", instead of speaking of themselves as if they're something or someone else.
There's a big difference between saying "we support" and "[brand name] supports", so why would we ever choose the latter?
Is it lack of confidence? Lack of commitment? Lack of passion? Maybe it's just a simple matter of never stopping to think, "why are we doing this like this?".
Speaking of yourself in third person makes you look nothing short of a pompous brat. Unless of course that's how you intend your target market to look at you.