Why?
The joke is self explanatory plus the doctor had to create hair for Seven so he has some experience
Though he does make a lot of jokes about his baldness and I distinctly remember an interview with Gene Rodenberry and Patrick Stewart where they were was asked....."is it realistic that baldness wouldn't have been cured by the time of TNG"....and Roddenberry replied....."in the future people won't care"
Seems that the bald jokes on Voyager would contradict that
The joke is self explanatory plus the doctor had to create hair for Seven so he has some experience
Though he does make a lot of jokes about his baldness and I distinctly remember an interview with Gene Rodenberry and Patrick Stewart where they were was asked....."is it realistic that baldness wouldn't have been cured by the time of TNG"....and Roddenberry replied....."in the future people won't care"
Seems that the bald jokes on Voyager would contradict that