A dom collars a slave then bans that slave from communicating with others. Why?

I see two reasons for this. 1) the dom does not trust the slave to be faithful to him. If there is no trust, why was there a collaring? 2) The dom is insecure and feels others are a threat. If this is the case, is he really a master?

This topic is for discussion only. Thoughts are welcome. Flames will be cheerfully nuked.