First of all: yes, we can use the "copy page" function and then delete content not necessary.
But: unwillingly this is not how a user works. Most of the content-writer likes to / are addicted to use C'n'P (Ctrl-C / Ctrl-V).

Old {section} and {row}/{column} macros had a big advantage: layouted Content was able to be copied selective.

so: It would be great to get a possibility, to "copy selection including applied layout"

Might be implemented as:

• copy a single section from a page with all columns
• Ctrl-A not just selects the active layout column content but the complete page

Current known "workarounds": (not applicable to "normal" users!)

• use labs source editor plugin https://marketplace.atlassian.com/plugins/com.atlassian.confluence.plugins.editor.confluence-source-editor
• edit / copy content via WebDAV

P.S: hope this is no duplicate, but can't even find any matching issue