I generally don't either, but I wonder: are you more comfortable with running a docker image without internet access? You can firewall your host so the container can't access it and assign an internal network to the container.
Well, I don't want to run untrusted apps for a start. I am not that desperate :)
Just read all the source code
Genuine question: what do you consider "trusted" code/apps? What difference is there between compiling from source and using the prebuilt official Docker image?