You assume that these UI’s were actually “designed.”
If the developer of something like that spent as little time designing his software as he did his GUI, the product would have never made it out the door.
The problem is that UI’s are mocked up for testing purposes and then deprioritized until there is no time left for them. Designing an easy to use UI takes exactly the same process as designing the rest of the system - talk to the users, do some research, build, test, and repeat. A developer or a graphic artist/designer will do just as well there.
Now, if you want it to be PRETTY as well as functional… yeah, get yourself to an artist.
I speak as a programmer who used to design UI’s a bit - I as a developer was the first person on the project who suggested we might as the people who would be most likely to use the software how they expected things to work