Is austerity necessary in Buddhism?
Is austerity [as defined above] necessary in Buddhism?

The answer depends as follows:  


As a householder, austerity, as you defined above, is not required since it's not part of the five essential precepts prescribed for him.1 However, this austerity, also know as the 8 precepts, is usually applied during retreats and Uposatha days.2  
As a monastic, it is required consistently since it will help to develop the meditation practice more effectively by diminishing unwholesome obsessions &amp; available distractions.


This distinction, however, is not "set in stone" or "black &amp; white" since householders are encouraged to follow this kind of austerity more consistently if they can and feel inclined to do so.