The problem is that orgs are not set in stone. Teams get merged and split in reorgs, buyouts and mergers happen, suddenly your microservices designed around "cleanly defined boundaries" no longer make any sense. Sure you can write completely new microservices but that is a distraction from delivering value to the end customer.

So? The solution is that services travel with teams. I've been through more than one reorg. That's what always happens. The point is to have clear ownership and prevent conflicts from too many people working on the same code.