Another thing DFC, if it's company policy to have 2 controllers in the tower at all times it is also no doubt a stipulation of their insurance. If a controller was to agree to man the tower on his own when two controllers are the requirement, HE/SHE is liable for any claim consequently made against the company because the insurance would be declared null and void and responsibility would transfer to the accepting party( at least in this jurisdiction it would). Things a little clearer now?