It's not lazy, it's by design. We have chat messages because the actual knowledge is stored inside of people, and chat messages are the most searchable way to see what people know outside of being able to ask them personally.
So why don't all of these people simply write it down in a notion/document store and meticulously keep it all up to date?
Because the business does not want that. We demand efficiency, so we understaff engineering departments sufficiently that there is always a little crunch, so that slightly-too-few engineers have to work slightly-harder-than-they-want to make the business successful. The end result of this intentionally engineered "lack of time" is that things like maintaining meticulous documentation are ignored, and the only time the knowledge is shared is in a frantic slack message.
The business is designed to do this. It's not laziness. It's the standard operating procedure to increase efficiency and profit.