Why is Ubuntu default to allow everyone access to other users folders, Admin or Standard?

Solution 1:

According to the security team policy:

By default, Ubuntu is designed to allow users to easily share files and help each other (see bug 48734). To support this, each user's default home directory is readable by all other users. Private files could be kept in the "Private" sub-directory, where access permissions can be set to limit access by other users (mode 0700). If restrictive home directory permissions are a priority for your system, please investigate the /etc/adduser.conf file for adjusting various settings when creating new users, including the default permission mask for newly created home directories.

Solution 2:

While it would be nice to have most of your files invisible, it would be impractical for situations where you need read access to to the files (for example in recovering files, or in copying the files to another system) but do not have access to the account (lost password, unable to login because of bad settings, etc).

Remember, no one can write to your folders by default unless they are logged in as root, logged in as you, a member of your group, or running a live CD.