Sometimes they are in such a rush, they can forget. One of my friends lost her cat (I believe she had several) in the mad scramble. Sometimes the pets freak out and cannot be found.
Most people in Paradise had no warning and had to leave with nothing more than the clothes on their back. I'd imagine anyone who wasn't at home when the fire came through wasn't going to be able to run back to retrieve their pets.
I'd have two choices. Stay and help my wife grab our dogs or leave all of them behind wife included. So I might die trying to get the dogs. Luckily I can grab them all in under a minute.
in 2014 when we had to evacuate because of the Cocos fire - I made sure I knew where the dog was in advance in case we needed to evacuate (she got some beach time out of it). But, the old girl (RIP) was known to do a Houdini trick every once in a while. I can assure you that if there is fire barreling towards the house and the dog is missing, I am taking my kids and getting out of there no matter what. My understanding is that the Paradise fire was a last minute thing where people had to run for their lives (and many did not manage to). I can understand this. FWIW - We have critical conditions here today and tomorrow. Got my to-go bag ready in case something happens (hope it does not).
Sometimes they're running when they leave. There were some people who were burned alive because they couldn't run.