Essentially, this service is for those people who want to take a dog on a walk but don't want the other responsibilities of ownership, or don't have time for them, or don't have room in their homes for a pet.
I gotta tell you this is essentially animal prostitution. Get your mind out of the gutter. I'm not suggesting anything sexual between these folks and the rent-a-dogs. But I am saying that such an impersonal relationship, purchased on an hourly or daily basis is extremely similar.
If you don't want a pet don't get one. If you don't have room for a pet, don't get one. If you just want to see animals for an hour or two or a day at a time,, go to the zoo. If you want to get up close and personal with those animals, go to a petting zoo. But to rent a dog for short-term, temporary companionship? Those dogs are getting pimped and the renters are sort of like Johns.
And I say this as a non-tree hugger, as someone who knows the difference between humans and animals. But as my grandma would say, this service is triflin'.