Handmade (Gay) asked if all German mothers sew their children's carnival costumes. Not at all. Most costumes are store-bought, and you can indeed buy them everywhere: the grocery store, ALDI, department stores, toy stores... And there is at least one huge specialty shop in Cologne that has every costume, uniform, and all the props imaginable.
Judging from the online sewing community and the very lively fabric markets, it may seem as if a lot of people sew, but I personally only know (of) a couple who do. One of these is a cousin of mine who, along with me, sort of continues our family's tradition.
When my mother and her four sisters were little, they had no money for clothes, but my grandma sewed them matching dresses for all major occasions (sewing at night when the family was asleep). Later, all but one sister sewed and made each other suits and dresses. My mother told me recently that the one sister who didn't sew was the most fastidious; everything had to be sewn "just so"!
When I was little, my mother sometimes made holiday dresses for me, and she sewed for my grandma who by then had shrunk a bit, with a rounded back, and therefore couldn't wear RTW. When I got older, I started to sew a little, but also started "ordering clothes" from my mother, so much better than trying to find RTW that has the right styles and colors.
When I was a teenager and about to go on a foreign exchange year in the USA, she sewed me a small wardrobe, a couple of shirts, very short shorts (that I wasn't allowed to wear at an American high school, of course!), and a shiny brocade skirt for dress-up. In hindsight this was an unusually high number of home-sewn garments; maybe she wanted to send as much of her with her almost 16-year-old daughter as she could!
These days, I hear the usual "You know you could buy something like this very cheaply, don't you?", but she also takes a lively interest in everything I make and sometimes even sits with me and helps me put the finishing touches on a garment.
We also share one sewing machine. She always had a treadle machine with zig zag stitching as the most sophisticated feature. About fifteen years ago my dad gifted her an electric machine. When I wished for one as well, she offered to let me have it; I only have to give it back for a day now and then when she has new curtains or so; other than home dec she hasn't done any sewing in a long time.
And it's only the internet sewing community that's made me realize that a 15 yo non-brand sewing machine isn't the height of technical sophistication!