text: I think its probably like the women's ordination argument (into which fray I will not wade, nor is this an invitation, to anyone reading this, to debate).
  We know some things about what Jesus did and the Magisterium feels that it has no authority to go beyond that.  I think there are any number of cultural variations that one might hold up as local, possibly significant, alternatives, yet these are not what Jesus chose.  Had He wanted, He could have chosen a fish or egg or anything globally common as matter for the Eucharist; why He chose bread and wine I won't pretend to know.
  There is nothing undignified about beer and pretzels, but you may substitute Hydrox for Oreo's, as you see fit.