DOCKER commit is creating larger/huge images

My initial “docker image” when I build from my dockerfile is just 400M.
I ran my container from it. After few days, There were no much changes in the containers expect modifying few files.

But when I saved my running container in it’s state using “docker commit” it is giving a image of 5G+. Docker export even creating a huge volume. Wondering what could be the cause!

I checked docker history even.
Any pointers ?