>>149895829
Live animals are hard to work with. Require special handlers, their own food and water separate from the normal catering bill, and they can be unpredictable even if well trained. Plus if you use a live animal then you are going to have to create multiple dummies / puppets of it for stunts the live animal can't (or won't) do, or else just use CGI anyway. In the case of the former, you're strictly limited on how you can use the animal since dummies and puppets can only stand in for so much, and if you're using CGI, alternating between CGI and real is more jarring than just doing full CGI from the start.
And if you do full CGI from the start you can make the dog behave exactly as you want in every scene without hours and hours of training and coaching.