This is all spitballing, but I'd wager it's a third the type of workloads, a third hedging against your business depending on a single external provider, and a third trust.
Not everybody is coding or doing work that lends itself to burning tokens for warmth. Reuters for example seems to be more interested in using it for research, editing and formatting citations and the like. There's only so much of that work that needs doing, it doesn't always need to be real-time, and they probably don't see it scaling exponentially. They also need to be very aware and in control of their model's biases, or they risk it compromising their work output.
It's widely expected that all of the major providers will need to - and surely want to - drastically raise prices to justify the ludicrous amount of capital they're burning. Multiple companies have already talked about how their AI costs have exploded, and from what I understand that scale of enterprise is paying API rates. I would be disappointed if big business wasn't having a think about what that liability could look like. It's one thing to be reliant on a relatively "stable" vendor like Microsoft for Windows and Office, another to get AWS sticker shock, and then this is promising to be an order of magnitude worse.
Then just plain trust. What if ChatGPT starts recommending your competitors products, or the USA bars export of Anthropic's latest model (again, but for real this time), or they stop serving a model your business now depends on, and so on... That's a lot of risk to leave outside of your control.