Using office 365 reduces risk of network problems in an office. Its very time efficient when using applications such as skype for business video conferencing and hosted email exchange. Office 365 apps also reduces the number of severs and computer resources, which lowers the cost for business. It's also a great disaster recovery contingency as if your computers & devices in your office where unavailable you would still be able to use 365's online resources.
Putting your e-mail in the cloud instead of on premise will prevent your whole business going down in the event of power cut or floods, so you can connect from anywhere to your emails