That's reasonable as you can already download those files and they would likely bloat the takeout into being a miserable experience.

The confusing part is that you can select to include data for Google Drive with the text:

> Files that you own that have been stored in your My drive and computers. More info

Only two levels into the help text there's mention of what is included - but no explicit mention that uploaded/shared files are excluded.

The entire (empty) folder structure is there, so it's easy to think the files are too.