Business travel and multiple offices can make data backup a particular challenge.
As a consultant working from home or at a client site, as a sales person or any individual that works in multiple locations, you have to ensure that your data is safe and available. Your business may or may not have a corporate backup solution in place - but it unlikely to be effective and efficient for you. You spend too much of your time away from the office to store your data on central file servers.
The very nature of a person that travels also means that the data is more vulnerable - either on a home-office PC or on a laptop. Theft from the car or at the airport, physical damage from being dropped, mishandled, abused, extra wear-and-tear of hard disks, spilt coffee!
The data you have is often sensitive. It can be client contact records, sales presentation, proposals or client based work and often the data is time-critical - you need it for the client presentation in one hour! So when a file is lost, you cannot afford to wait for it to be recovered.