It's not if you need it or not; but how you use reinforcement.
Mounting heavy steel way beds may require reinforcement support however; it depends on the design.
If the design requires vibration damping and reinforcement; you must make sure that the reinforcement/support does not couple any vibration source to another or the machines feet. (e.g., coupling the way beds together)
In essence; coupling one object to another using reinforcement is effectively coupling vibration as well, while there is some damping, it's not optimal.
Look at patent: 5,765,818 for some visual examples
-Jack