Ever been to a tailgate at a midwestern university for a November football game? You'll see thousands happily eating and drinking, often in temperatures much lower than 40 degrees.
Go to the Alps. As long as the sun is out and the wind remains calm, even in the winter, most of the outdoor seating at the mountain chalet restaurants will be occupied during meal times and apres-ski. Often by families with young children. Well, maybe fewer children apres-ski...
My wife and I often go to nearby Stowe to walk with our toddler and dogs along the nice paved trail the town maintains. We usually take lunch and eat it at a little park along the trail that has several picnic tables. If it's lunch time, we're usually far from the only ones eating there. We generally only stop going when the snow accumulation gets too deep for our son to walk. But I often see snowshoers and cross-country skiers eating there even in the depth of winter, which in Vermont, is far, far colder than 40 degrees.
So, yes, many of us do eat outside in the 40s and even colder sometimes. Winter is too much fun to stay indoors all season.