Why do not provide Unreal Engine as docker image?

I guess it’ll be very easy to build on different systems. I mean to compile Unreal Engine in docker container and then move Unreal Engine to the host system

It would be indeed nice to have a built docker image to download, but since there is not such thing due to source license, you can build it from GitHub - tweakmy/ue4-in-docker: Ease of build for ue4 for people who only wants to play with ue4editor like me

more info
https://forums.unrealengine.com/development-discussion/engine-source-github/38998-dockerize-unreal-engine-4-for-linux

Check this out for a modern and seemingly much more fleshed out docker support for Unreal