Necessary to neuter your male pets? Yes, unless you're a breeder.
Necessary to implant fake balls? Well, they argue that the pet will be fooled into thinking he still has his jewels. I think the animal will figure out they're falsies sooner or later. So, it depends on how dumb he is.
Personally, I think this is extremely fucked up. Of course, I think having a friend that you can lock up when you're not using him is pretty fucked up too.