The main reason for choosing a dedicated server hosting is exclusivity and full control over the resources of the entire server. With a dedicated server, you do not share any resources such as bandwidth, hard disk storage, memory, etc with anyone else and can also customize your own security applications and protocols with total control.
A dedicated server is like owning an independent house, whereas a VPS is like owning an apartment in an apartment complex. When you are in an apartment, you do have limitations ( ie: can’t remove the roof if you want ) even if you own your own space inside of that building. Whereas if you have an independent home you have absolute control.