Summary: boldface came first, in print, and was widely used. Much later, some mathematicians started to write blackboard bold on blackboards (because actual bold would be very untoward to write on a blackboard). Then, the usage was backported to print.
I find it ugly, a sort of breaking "suspension of disbelief", I don't know how to explain why. Some sort of "anachronistic" feeling, like watching a movie about the roman empire and some soldiers wear watches.
EDIT: as for having "different symbols", this is not the case. They are exactly the same symbol, with different faces. Like when you write the letters "a" or "g" very different on a blackboard as they appear on print.
https://en.wikipedia.org/wiki/Blackboard_bold
Summary: boldface came first, in print, and was widely used. Much later, some mathematicians started to write blackboard bold on blackboards (because actual bold would be very untoward to write on a blackboard). Then, the usage was backported to print.
I find it ugly, a sort of breaking "suspension of disbelief", I don't know how to explain why. Some sort of "anachronistic" feeling, like watching a movie about the roman empire and some soldiers wear watches.
EDIT: as for having "different symbols", this is not the case. They are exactly the same symbol, with different faces. Like when you write the letters "a" or "g" very different on a blackboard as they appear on print.