While it is clear that self-driving cars won't have steering wheels in the future, these prototypes are jumping the gun and a waste of time. As Waymo quickly realized, you can iterate much faster staying away from these futuristic prototypes.
[0] https://qz.com/1005083/the-cutest-thing-google-has-ever-made...
Cruise has one advantage that Waymo didn't - General Motors. They don't need to build an automotive product development and manufacturing org from scratch; it's already there and it's got a hundred years of institutional memory.
Since GM has been working on things like this for decades, I imagine it gives Cruise the opportunity innovate on the vehicle itself quite capably without taking their eye off the ball.
The point still stands that it's mostly a waste of time and resources while we are still years away from fully functioning self-driving cars. You could argue that if GM has artists and designers who are bored and need a side project, it may be worth the news cycle generated by the reveal, but other than that it doesn't add much to the conversation.
There have been plenty of such prototypes; just at CES a few weeks ago, LG had an almost identical prototype [0].