You wouldn’t but in any decent sized organization you will have to. If it is an organization that needs to exist there will be some common set of critical data.
You DO have to share data in other ways, usually datawarehouse or services, but that is not the same thing.
I’m not saying literally every source of data has to be shared and centrally managed. I’m also not saying “rdbms accessed via traditional client and queried via sql” when I say database. I’m just saying a shared database of some shape is inevitable.
Also, operationally it’s not “semantics” at all. You don’t get into (many) operational problems with analysts sharing a datawarehouse. You absolutely do with online apps sharing a rdbms, they aren’t the same thing.
A data warehouse is a type of database and is does need to be managed. Your assertion that it is easier to manage is orthogonal to my assertion that there will always be a central database to manage in an organization of decent size.