Helm upgrade doesn't pull new container

Helm will roll out changes to kubernetes objects only if there are changes to roll out. If you use :latest there is no change to be applied to the deployment file, ergo no pods will rolling update. To keep using latest, you need to add something (ie. label with sha / version) that will change and cause deployment to get updated by helm. Also keep in mind that you will usualy need ImagePullPolicy: Always as well.