Many many things about colocation services
Server colocation facilities offer surge protection and battery and generator power to assure that resources will not go down due to electrical events. Additionally, they have personnel to intervene when equipment goes offline for whatever reason. Better internet connectivity is also one of the reasons businesses decide to outsource their data support and hosting functions. A company can get more bandwidth with server colocation without having to pay what it would to have it in house. A company can choose various services with server colocation.