Why doesn't docker file include asset pre-compilation or migrations?

Hey everyone, 

I just finished deploying Jumpstart Pro to Elastic Beanstalk on AWS using Docker. One of the things I changed in the sample Dockerfile was to add a couple of RUN commands for compiling assets and always running migrations. Curious why this wasn't in the sample file. Is there another/better way to do it that I'm not aware of? 

Thanks