Because teacher Christa McAuliffe was onboard. I believe they previously broadcast earlier shuttle launches, but by 1986 they were no longer novel; putting a teacher onboard who was planning to teach some lessons in space made educators more interested and so many schools pulled out the TVs to show the launch live. Turned out to be a different kind of education than they expected.

Plus with almost everyone being related, men don’t have to play that “imagine it was your sister or daughter” game to generate empathy for women. /s