Two advantages:
* Security: the container is a sandbox, so if it get hacked, the damage is limited to the container and not the whole system.
* Repeatability:  with a container, you can have a known system that has everything you need for your application and little to no extra cruft, so you can compile, run and debug your apps in a more consistant way.  You don't have to worry about hundreds of different types of linux distributions or windows setups that have become 'unique' over time.