There are several reasons why it might be necessary to hire such a service.
First and foremost, man and van services are professional and experienced in the moving process. They have the necessary equipment, such as dollies and straps, to safely and efficiently move your belongings. 
Man and van services also offer convenience and flexibility. They can often accommodate last-minute or unexpected moves, and can work around your schedule to make the moving process as smooth as possible. 
Another reason to hire a man and van service is if you do not have a large vehicle or are unable to transport large items, such as furniture, on your own. These services are equipped with larger vans or trucks that can accommodate all of your belongings, saving you the hassle of trying to find a way to transport them yourself.