Today we begin our study of Massechet Ketubot (1:1) which informs us in its opening Mishna that the marriage of a בתולה (virgin) traditionally occurred on a Wednesday. As the Gemara proceeds to explain (Ketubot 2a), this was established to provide a quick resolution to any טענת בתולים (claim made by the groom following the wedding night querying his wife having been a virgin when they married) because the Beit Din traditionally met on a Monday and Thursday. And since weddings require preparation, it was better to marry mid-week than on a Sunday since Shabbat would impede some of those preparations.
Interestingly, later on in the Gemara (Ketubot 3a) we are told that in communities where the Beit Din met daily, the concern expressed by our Mishna is no longer relevant. Yet notwithstanding this, logic would dictate that the one day on which weddings would not take place, other than Shabbat itself, would be a Friday since the Beit Din does not sit on Shabbat.
Admittedly, as the Tur (Even HaEzer 64) explains while quoting his father Rabbeinu Asher, a טענת בתולים can in fact be made even on Shabbat. Still, one would have expected that there be opposition to Friday weddings. Nevertheless, as Israel Abrahams records in his ‘Jewish Life in the Middle Ages’ (p. 186), ‘the favourite wedding day in the Middle Ages was Friday’.
It should be noted that the Rambam (Hilchot Ishut 10:14), basing himself on Ketubot 5a, opposed this practice for fear that it may lead to chillul Shabbat. This is because when a wedding was held on a Friday, the wedding feast often occurred on Friday night, and in the situation where more guests would arrive than were expected, there may be a temptation to prepare food on Shabbat and thereby transgress Shabbat.
However, notwithstanding these concerns, Friday became the popular day for weddings especially in Ashkenazic communities, and while a number of justifications have been offered for this practice (see Drisha note 13 on Even HaEzer 64), the primary reason – as noted by the Mordechai (Ketubot 129) – is משום תקנת עניים, meaning that out of concern for the poor for whom it was more economically viable for their Shabbat meal to double as a wedding feast, Friday weddings became halachically justified. What this comes to show us is that while there may be halachic preference for certain practices, social and economic pressures can often lead to alternative conclusions.