It's splashier this way, and is meant to shape the narrative, make other companies fear their warchest, and make hiring easier. Of course, those who are in-the-know won't be fooled, but the perception of the general public will be set in stone by the PR framing.
Most people won’t look at the structure, they’ll just internalize that OpenAI is massively funded.
That effect kicks in well before the money actually does.