If you had the sterotypical American mom, she told you to wear your best underwear in case you were in an accident. Like it will really matter to the paramedic that you have the best undies. Depending on the accident, they might have to cut them off of you and then where would you be. Right one nice pair of skivvies short.
Well in France, you certainly need to wear your best. Not because of the ever fear that disaster could strike at any moments, but it's the rule of the line. The clothes drying line. I am not sure about all French people, but my French relatives dry their clothes on a line (even in the winter) and only use the dry under emergency situations -- ie several days of rain. Well if you live in Paris, this emergency situation could be more common. So in order for your in-laws -- well mine anyway -- not to see your old cotton undies faded with time, I have to break out the nice pairs. Last year I specifically went underwear shopping before my European departure, since I wasn't sure I wouldn't be laughed out of the country. This year, so such luck, but that's ok. I think I am doing ok. There was that one close call though with my FIL insisting on helping me hang 'the kids' clothes. While I am sure he was being nice, I had to quickly pick out anything that looked scandalous to hang myself.
Fashion standards are alive and well -- even for the unmentionables.