Kugel is generally regarded as a 'traditional' Jewish food. But the Conversations in Klal blog is running an exposé: Kugel was not actually that common in the homes of our European ancestors (for those of us who have European ancestors...). The blog explains that it was incredibly difficult to keep food warm over Shabbat and that most food was eaten cold:
Stoves in pre-War Europe were coal fed or wood fed. The more time you spent in cooking, the more fuel you had to feed that stove. Those home stoves could not be fed fuel right before Shabbos and remain hot until after the mid-day meal on Shabbos. Some people, those with more money, would have special niches built into the side of the fireplaces they used for heating their rooms, niches that a pot could go into to stay warm. Those fireplaces were larger and before Shabbos wood could be added and the fire banked so that there would be warmth throughout the night and into the next day. That was during cold weather. When the weather turned warmer, such that the house was not being heated, there was no fireplace niche to keep food warm.
Some people would rely on a local bakery for warm food for Shabbos. The fireplaces in these bakeries were oversized, resulting in large baking slots above the fireplace. Many people would bring their pots of food to the bakery before Shabbos to be inserted in one of these slots to keep warm over night. There was a charge for this bakery use, and not everybody could afford it.
Kugels were not wrapped up in foil paper as many are today--ask your grandmother if she had foil paper at home in Europe. The kugels were placed into the cholent to keep warm, for those who had cholent. They were not the consistency of the kugels we see today.
And yes, another method of keeping things warm was to take a hot pot right before Shabbos started and wrap it up in a feather bed. Also not available to everyone, because a feather bed, certainly an extra feather bed, was a luxury.
So, did our ancestors in Europe eat kugel every Shabbos, and we're just continuing their custom? Not likely. Some may have eaten it on Shabbos during cold weather, or maybe not. The "kugels" that ended up inside of a cholent pot for Shabbos did not resemble what we call kugel today, and many of those cholent kugels were not made with potatoes at all, but with flour. The wealthy or well to do had some options that whole swathes of the rest did not have. And in the hot weather months cold food on Shabbos was the rule and hot the rare exception.
I knew that traditionally chulent was cooked overnight in bakers' ovens but honestly, had never really thought about why households couldn't cook it at home. I am kind of upset to realise that all of those meat and fish delicacies referred to in our shabbat zemirot (and it's astonishing how many of them do actually refer to food) were eaten stone cold...