Because the dog needs to be walked several times a day, whether you need to work late / go on holiday in a non pet friendly place / go out that night / wake up late, or not.
Is it cheaper to buy a robot, than just hire a dog walker?
I love my dog, but I work and It would be nice to have someone come to my house in the middle of the day to interact with her. Take her for a walk and make sure she didn't accidentally flip over her water bowl, etc. It would be peace of mind for me and entertainment for her.
There are lots of situations when you have to leave your home and you can't take your dog with you or it would be very difficult to handle.
Our society is at a point where it can debate having robot butlers for our cats.
What a wasteful time to be alive.
It's still more useful than what 90% of startups are doing, so I wouldn't complain about it. Being able to provide care and entertainment for pets in situations in which you can't be with them is not a bad thing.
If the alternative is for the dog to poo in your flat...