I'm not sure of the details, but I think it's for two main reasons. The first is that the early Reformers sought to distance themselves from the structures of the Catholic Church, which would include monasteries and the like. They were setting up their own structures instead, so they didn't inherit the old ones. The second is that the Protestants were theologically opposed to the idea of different classes of Christians. They rejected the notion of the priesthood, at least in the Catholic sense, believing instead in the priesthood of all believers. Similarly, they rejected the idea that some people were called to a more ascetic lifestyle. Thus Luther himself, although a priest and an Augustinian friar, got married. Still, it's interesting that Protestantism still did develop many movements which might be considered akin to watered-down versions of monasticism - or perhaps like the Franciscan Third Order. The various communes of the Pietists, like Herrnhut, or the Pietist conventicles or Methodist societies could be considered - not monasticism as such - but an expression of similar urges to those that, in an earlier age, had contributed to monasticism. No-one really knows. Obviously the date coincides roughly with various winter festivals of antiquity, but to say it's simply the solstice celebration must be wrong given that Christmas doesn't fall on the solstice (which is around 21 December now, and in the Roman calendar was 24 December). John Chrysostom suggested that the date had been chosen because it fell halfway between Saturnalia and New Year, so it gave the Christians something to celebrate while the pagans were recovering from Saturnalia and preparing for New Year. And I suppose that's as good a guess as any. Obviously the date was established before Christianity got much of a foothold in northern European cultures, so although Christmas acquired many of the traditions of the northern midwinter festivals, its date can't have been influenced by them. What the others said. I must mention, however, the Quartodeciman controversy, which was important to all this. The Quartodecimans celebrated Easter on literally the same day as the Jewish Passover (which was on 14-15 Nisan, and could fall on any day of the week). Other Christians celebrated Easter on a Sunday at around the same time (calculated in an unnecessarily complicated way, as already mentioned). There was fierce controversy over this which was theoretically settled by the Council of Nicaea in AD 325, but which obviously continued to rage anyway since it took a long time for everyone to accept Nicaea. In England it remained famously unsettled until the Synod of Whitby in AD 664. The issue was considered important not simply because of ecclesiastical order, but because the Quartodecimans, by timing Easter to coincide exactly with Passover, were considered to be falling into a Judaising heresy. I've no idea about that sort of thing. I think that assuming that these things go back to fertility celebrations or the like is a bit rash though - you just never know. I'm sure not everyone in extreme antiquity was so obsessed with fertility (and with ancestors) as western anthropologists have stereotypically assumed in the past.