Counter Terrorist - They are here to make communications with main base. Actually, they have stored data about Terrorist activities nearby the area and data is being send to Headquarters. So, it is vital for them to save communication units from Terrorists.
Terrorists - Terrorists knows that if data is transferred to CTs Headquarters then it is possible that one day army would attack their base. As they will know about Terrorists activities and hiding spots. Then it is easy to conquer them. So, Terrorists have to break communications between them.