White women spend hours on their hair, daily. Just because your BFF doesn't spend as much time doesn't mean it's a "Black thing." A White colleague washes and blows out her hair every day and told me it takes an hour. The Blow Dry bars allot 45 minutes per client for blow outs so you know doing them at home takes longer.....and that is every day. My coworkers hair is BSL, thick and wavy but she likes it straight. Then she has to do her makeup, which she packs on, so she is up at least 2 hours before any meetings we have to attend.
I doubt that many Black women are spending 7 hours a week on their hair.
I'm in crochet braids that took about 2 hours to install (my hair was already braided). I shake and go in less than 2 minutes, daily. I spend 10 - 20 minutes once per week trimming out the frizzing parts and 5 minutes or so per night moisturizing my own hair. I keep them in for 2 months at a time. All in all I spend about 1 hour per week on my hair, not counting the installation/removal time.