No event can happen unless it is organised first. Whether it is easy to organise or not will depend on what kind of event you are having. For instance a simple birthday party with friends and family will be easier to organise than a wedding reception for 400. But one thing they have in common is the need for a dj, so you have plenty of music and someone to play it.
Hiring a professional dj is also good if you need an MC as many disc jockeys also add that talent to their list of skills. Having a Master of Ceremonies takes a great deal of pressure off the host who then has time to meet and greet the guests without worrying about having to guide the event along.