Tell that to my smallest dog, ha! She has no problem holding it in... as long as you're watching. Unsupervised, the indoors is her toilet. (To be fair, the shelter/her foster family did note that this was an issue with her.)
I've never had cats (babysat some, but that doesn't count) so only answering for dogs.
Setting up for dogs is faster I think, at least I've never had an issue just taking home a dog at a moment's notice (twice I've called my husband at work and told him to be ready to go to the shelter to meet...