Remember the ringtone Maxima assigned to Sydney? "They're coming to take me away." And more than one other character has described her as being ... a bit unhinged.
Or there's a more charitable explanation; they don't want Sydney to get hurt if Lapha manages full control and tries to batter her way out.

Maybe they wanted to keep both the orbs and their anchor in clear view of security cameras at all times, and were worried as to what might happen if they taxed the tether connecting them too much. A (bulletproof?) glass box seems like a happy alternative.