If people knew how many brand new servers have hard drive failures, they wouldn't be able to sleep at night without knowing they have several backups of their critical data. Many times the critical data is stored in Hyper-V virtual machines.
While the new Windows Server 2012 R2 and newer versions of Hyper-V allow snapshots aka checkpoints to reside on a separate hard drive, those files are still interdependent and interrelated.
Hence, it's impossible to get the VM up and running if any of those hard drives should fail.
Apart from the fact that Hyper-V snapshots and checkpoints are huge performance killers, Microsoft itself recommends against using them on production systems for several reasons. First is the already mentioned huge performance penalty involved with snapshots. Second, checkpoints aren't portable as plain VHDs are. They depend on CPU and hardware architecture. And third, Microsoft has to deal with plenty of bugs related to snapshot handling and you wouldn't want to add that risk on top of all hard drive failure risks.
A RAID array isn't going to help much with data corruption risks resulting from OS software bugs either. In addition, by the time it is discovered that a hard disk issue is present, the damage is already done and replicated by the RAID. Snapshots are more likely to cause hard drive failure, too, due to the higher disk I/O they cause. The wear on the hard drive is hence greater.
A Hyper-V Backup on the other hand takes a copy of the entire VM, with checkpoints or without. It's important to use a new media for your backups, such as an external hard drive connected via USB, a network share, a NAS device, or a remote FTP server, for example. You would want to copy your VMs to another isolated machine, which isn't connected in any way with the original.
Think about electric discharge, electric surges, virus damage, software corruption, and mechanical failures due to overheating or wear and tear, are likely to affect the entire server. A RAID array is also likely to break with several disks damaged simultaneously since they are exposed to the same conditions and life time. If you Hyper-V backup is stored on a separate box, chances are greater it won't be affected by all of the above. Hyper-V backup is different from Hyper-V checkpoints in that it isolates the VM and clones it in its entirety on a separate system.
While you can work productively without snapshots and checkpoints, you can't without solid, reliable, and frequent Hyper-V backups, since backups are the only insurance you have against data loss.