I’ve seen companies get sued and lose in court for copying UIs. So no, legally speaking, copying a UI is not something that companies ignore.
The look and feel of an interface could be covered under a design patent, which would be a different question than copyright, and a much higher bar to enforce (particularly, protection is far from automatic).
Can you point to cases so I can google them?
The look and feel of an interface could be covered under a design patent, which would be a different question than copyright, and a much higher bar to enforce (particularly, protection is far from automatic).