Some things I’m curious about

• Why do some dentist offices call themselves “<Name> Family Dentistry”? They don’t even see everyone in the family – you need a pediatric dentist to see the kids.
• Why does the hair on my chest, legs, and arms get to a certain length and then stop growing, whereas the ones on my head keep growing and have to be cut?
• Why is the bean with a black spot on it called “black-eyed pea” and not “black-eyed bean”?
• What’s the origin of the term “a flight of stairs”? Specifically, how did the term “flight” come to represent an uninterrupted series of steps? Is there a definition of how long a “flight” is? I came across a description of a hike that described the elevation gain being “equivalent to climbing 65 flights of stairs”. I can tell that’s not trivial, but I don’t know how high it is.
• Why is the Gregorian calendar organized the way it is? For instance, why is February the shortest month instead of, say, July? Why does February get the extra day on a leap year? Why are months that have 31 days interspersed among ones that have 30?
• Why do some people brush their teeth before they eat breakfast? Isn’t eating breakfast going to deposit bits of food in their teeth, and brushing afterward can both clean them out and leave them with the fresh feeling?
• How does a blind person who can read using Braille know where to put their hands in order to read?
• What’s the origin of the term “back-of-the-envelope”, as in “a back-of-the-envelope calculation”? The expression “back of a napkin” is similar, and I can see how that evokes the notion of just wanting to jot something down quickly during a meal where a napkin was the only available medium to write on. But “back-of-the-envelope” …? Was there a time when envelopes were more prevalent around our living spaces, such that one could reach for an envelope quicker than they could reach for regular paper? Supposedly you’d need paper to write on and put in an envelope, so I find that surprising.
• Why are the light switches for some bathrooms outside the room?
• Why do establishments that have single occupancy bathrooms still designate genders to each bathroom? If there’s only ever going to be one person in there anyway, does their gender matter?
• I took a domestic flight in Turkey where the entire flight crew was Turkish. Yet the announcements intended solely for the crew (“arm doors and cross-check”, “cabin crew please be seated for takeoff”, etc.) were still in English. Why? If the point of the announcements are to communicate clearly among the crew, and you know the entire crew has a language besides English as their mother tongue, why not use that language?
• The “No entry” road sign in Norway is actually curved (see below). Why? Is it so that the sign can be seen from a wider angle? But the odd part is that I only noticed this sign being curved. If visibility was such a priority other signs would be curved too, no?