[johannes1234321]

A factor is, that the user's of those apps overproportionally create content, which is later served to other users.

Most users come via Google or other ways to read some content. Only few participate actively. Earning less on those few users can be valuable overall.

[bottlepalm]

'users of those apps over proportionally create content' - really? prove it. Second, posting a link is not the same as 'creating content'

[johannes1234321]

That is content for the site. Without that link post reddit would be less attractive.