All Saints From The Golden Legend (1260):

"The second purpose of the feast is to supply for omissions. We have in fact omitted many saints, not celebrating feast days or making memorials of them. Indeed we could not have feasts for all the saints. For one thing the number of them has multiplied until it is almost infinite. Besides that, we are weak and because of our weakness could not put up with so many celebrations.... Therefore the Church with good reason has ordered that since we cannot solemnize the saints one by one, we shall at least honor them generally and all together."

What delightful thoughts. We celebrate All Hallows' because the number of people God has brought to Himself is surely near to infinite; and who could possibly take all that partying?