Some employees could browse internet through their personal connections and if there is no proper anti-virus software it is possible that some virus enters the system and then it could spread to the entire company.
Out Of Date Software
Software compatibility to the operating system is important; even if there is a business need to upgrade one of them the other should be compatible, if not there could be an issue in working and could affect any client deliverables.
There could be serious business impact if servers from one end of the globe are not accessible to offices in the other end. Such a setup involves hundreds of devices and also would involve third party internet service.