No not devout Christians. Few Christians now fast in Advent but most people have sung “On the first day of Christmas, my true love sent to me…”. The first day of Christmas is Christmas Day.
Until 20 or so years ago, 12th night parties were quite common. French patisseries sell galette de Rio, for 12th night. A lot of Christmas traditions were linked to the fact that little work could be done on farms in the middle of winter. Plough Monday was when they went back to work, ploughing the fields and it’s the first Monday after Epiphany, 12th night. When according to one of the gospels, the wise men presented gifts to Christ.
Winter was hard in the countryside and there wasn’t much work. When there wasn’t work, there was nothing to earn. A lot of the winter festivals and traditions were centred around extorting money, with various degrees of menaces. That’s why men blacked their faces, for example for the Cutty Wren tradition, and the St Stephen’s Day Hunt the Wren, and for poaching, to avoid recognition. This became a capital offence in 1723.
So religion is interwoven with convenience and necessity.