It’s a simple equation; voter apathy equals political indifference. Science is not a priority with the population at large, so why would the candidates risk a debate on science ? Not enough votes in it.
During the last US presidential election I heard someone interviewed who was voting Republican because Bush had ‘heart” and “heart” is what you need. Everything works out OK in the end if you have “heart”. I have to say my “heart” sank when I heard this. Compared to 'heart" hard thought and hard work is just no fun.