When the Sims 4 Cats & Dogs was announced, there was a bit of controversy surrounding the decision to make pets uncontrollable by the player. EA have explained this decision in a new blog post:
There are many factors at play here, some technical, some design, but in a nutshell, if players could see and control every aspect of their cat or dog, it made it difficult for us to make them do surprising, fun, and unexpected things. When we compared all the options, we knew that our game would be the most fun if we didn’t let players select cats and dogs, but instead gave you other ways to interact with them. When we made this decision, it fundamentally opened up things we could do with cats and dogs that we can’t do with Sims even!
Seems reasonable enough to me.