My brother was a lefty for everything except handwriting (his inability to operate a right-handed golf club was particularly striking). I suspect that he's mildly dyslexic, and found learning to write equally difficult with either hand, so went along with the default as taught.
I'm strongly right-handed, but there are fine motor skills I've learned to do amibdextrously as circumstances require, such as mousing and soldering. When I wore a watch I preferred it on my right wrist, because the left just seemed wrong.
I also reckon there are plenty of tasks where your non-dominant hand does more of the physical work. Certainly when riding a bike on dodgy surfaces, it's my left hand that clings to the bars for dear life.
I do wonder how it works for people like barakta, who are born with a significant difference in functionality between their hands. Is she right-handed because she's got a righty brain, or because her right hand is so much better that doing things right handed was always going to be easier?