I know of two cases where office water coolers are super useful: in areas with high temperatures where cold water is much better that the warm water coming out of the tap, and (if your model supports it) for getting a cup of hot water for tea. I've also seen them used in areas where the tap water tastes funny, but that's more of a patch.
However, neither of our statements are very useful as they are just anecdotes, a result of our personal experiences.
Even if you subjectively "feel" that spontaneous creativity is increased, these chats don't make companies more profitable. So I'm guessing that this "creativity" doesn't have much actual value, and forced in person work certainly has a high cost to the employee and society.
Hard to justify the cost/benefit.
I just realized it's worse than that. If the old adage on innovation "1% inspiration, 99% perspiration" is true, then water cooler simply cannot help much. Then, what you need for innovation (and not just a warm fuzzy feeling of a possibly good idea) is actual time to work on it, not a water cooler.
Second, I've not once in my life had a productive "water cooler" conversation. Not a single time, it's pretty much always just socialization about literally anything other than work. Same with lunch, people don't want to talk about work during their free time, and they don't. I've certainly never heard of anyone having a sudden eureka moment spontaneously like that either, and if they do these days they'll just post it in slack so that people can refer back to it rather than it disappearing into the ether as soon as the convo ends.
As for the idea thing, I can't say I've ever had many such a drastic PR where the approach was completely 180 degrees from what the PR is doing, and even in the rare occasions those do occur, both parties are usually more than okay with then hopping onto a short (meaning max 15 minutes, not some hour long monstrosity of a "quick chat") call to align.