Up until I was about 18, we always had formal Thanksgiving dinners. We'd spend all day cooking, then before dinner, we'd all get dressed in nice outfits or dresses. Then, after that year, we stopped hosting huge Thanksgiving dinners and would only have like four or five family members there: me, my mom, my sister, maybe my dad (parents are divorced) and an aunt. I have been wearing my stretchy sweat pants for Thanksgiving for the past 7 years! It's great! I prefer it casual.