Walter White in the pilot - full head of hair and a mustache - he's hapless, blown hither and thither on a wayward course by cancerous winds.
Walter White by the end of season 4 - shaved head and a goatee - large and in charge.
Walter White by the end of season 4 - shaved head and a goatee - large and in charge.
Although I'm struggling to think of many more examples of hairless protagonists outside Star Trek.
I also would have accepted the nerdier answer, which is that in the ST universe, humanity went through a whole genetic engineering craze (in the '90s!) that resulted in Khan and a lot of other madness. So we kind of avoided it after that, and just went au naturel with our gene pool.
The franchise actually did make a few attempts to circle back on this topic, usually as a convenient way of explaining why humans in the 24th century aren't all perfectly fit, hyperintelligent, post-Singularity badasses. Genetic engineering had become a taboo. This was highlighted in a DS9 episode, where Julian Bashir was hiding the fact that his parents GE'd his intelligence, coordination, etc. It was illegal, and he was worried he'd be kicked out of Starfleet.