The thing is, natural human hair can be brown, blonde, grey/white, ginger, and sometimes extremely dark, almost black (if I missed any type of natural hair please let me know). And for example, in my country, it is extremely rare to see blonde/ginger hair but brunettes/people with dark hair are everywhere, on the other hand, if I go to northern Europe it is rare to see brunettes but the blonde is usual. So you "not seeing" people with black hair is, most likely, because of the country you are in (of course this is just an assumption, I wouldn't know). My cousin told me that usually Asian people have very dark hair so seeing black hair is quite normal but it is rare to see blonde, for example.
I have very long curly hair and I usually wear it down, even with the wind so I don't think you can say it is convenient or not because that is something from your personal experience. Besides, even with it being inconvenient or not, you might prefer to have your hair down at all times, it is up to whatever you prefer. In the end, if you go against the wind it might be troublesome but if you go with the wind is nothing more than you feeling like a Vogue model!
Yes but keep in mind that hair dye is not something everyone has in their stories. So, for example, in my novel (which is based on a Kingdom with no magic), there are regular types of hair: blonde, brunette, grey/white, and ginger, however, there are three characters with unique hair: the MC that has black hair, the crown prince that has bright red hair and the MC's sister that has dark crimson hair. This is because I want to keep it somewhat "realistic" (even if I use these types of colors, I am trying to keep it as "normal" as I can) so I am not going to make a random kid be born with light blue hair making it look like cotton candy. And this is something I've seen in a lot of more "realistic" stories so far.
So, at the end of the day, it will depend on the type of story you are reading (not the thematic itself even though it helps).
Regarding the curls, ponytail, or braids, remember that those are nothing but looks that you can easily create (except the curls or wavy that can already come naturally) and, in this case, we are describing one of our female characters, and they can have several types of hairstyles during the novel. So, unless the character itself is always with a ponytail, braids, never letting her hair out, then it wouldn't make sense to use it as a description of the character.
This is just my thoughts on the matter since I feel that you are throwing all the black-haired characters in the same pot without taking into account the type of story they are inserted in. Everything I said, like everything in life, can be wrong, and if that is the case then please prove me otherwise, I would like to grow as a person but, so far, this is my opinion on the matter. No harm done!
