Modern server hardware has moved on. A single physical box is capable of many roles but why tie that server environment down? By Virtualising your server and infrastructure you open your business up to a lot of benefits.
Save energy. We all know its good to save energy and be a little greener. Virtual systems run less power consumption than traditional hardware driven environments.
Faster server provisioning. Need a new print server? 5 minutes. Need a test environment for a new application? 10 minutes. Reduced TCO as you already own the infrastructure.
Increase your DR capability and your server redundancy. Clustered server environments with shared storage are the bread and butter of today's Virtual environments and provide a higher level of redundancy and server up-time than ever before.
Need to patch servers? Shift the Virtual machine to another host and off you go.
Cleaner, faster and cheaper backups (and restore). Backing up Virtual systems is certainly simpler than ever before. Dump your VHD into the cloud and you can bring it back online anywhere with an internet connection and some file space.