Excuse me but this recommendation do not seem to me exact. If you consult the “Hardening WordPress” guide you can see this : “/wp-content/:
User-supplied content: intended to be writable by your user account and the web server process. ”
Then “wp-content” must be 770 and owned by user account and writable by Apache system user (this is valid for “wp-content” because there are some limitations for /themes and /plugins).
And then, if i have a shared installation, i can not create my web root with 775 permission because other users can see my files.