The department has a tradition of interaction supported by default file system permissions that allow others access to your files and directories. If you don't like this you are free to change your permissions (see the chmod command). Selective use of restricted permissions rather than locking your home directory is recommended.
There is tremendous value in being able to see how others set up account profiles, Xresources, etc. This value will be lost if people use this openness as an invitation to snoop.
Even if you restrict access to your account, system staff will make files related to the duties of TAs and GRAs available to instructors and research advisors on request.
System staff may also examine a user's files as needed to deal with system problems, system abuse or questions from that user.