It's because of important, writerly reasons, I promise.
What I love about both of these things is how surprisingly emotional they are. When I started watching Doctor Who, I thought I was signing up for campy, spacey fun, not hours of blinking tearfully at the screen, sad-babbling to my husband as I watched the Tenth Doctor regenerate. Same with Star Trek: Into Darkness. I thoroughly enjoyed the first installment (I typically enjoy all things J.J. Abrams) but I was not prepared for the EMOTIONS I had this time around. Bromance emotions.
So how do they do it? I don't have a definitive answer for this, and if I did, I'd open up a school called ALL THE ANSWERS FOR WRITING SCHOOL and rake in the cash. But my theory is this: that both the show and the film take the time to focus on the characters. What's fantastic about sci-fi is that you don't even realize that it's happening, because these important moments are generally happening while characters are doing things, running away from aliens and so forth. Elements of backstory (that the Doctor once had a family or that Spock is still aching from the loss of his planet) happen while other plot elements are going on. And our character's true motivations, their true capacities for fear/bravery/compassion/humor are revealed by the choices they make when in difficult situations. By taking the time--seconds in screen time--to give us glimpses of character, they plant the seeds for a huge emotional payoff. (Side note: Firefly and Lost are other examples of this being amazingly well-done.)
This is something that I'm not always able to put my finger on when it's lacking in books I read or movies I watch, and it's certainly not something I find easy to do in my own books. It's easy to get sucked into writing about the laser-guns and forget to write about the people holding the laser-guns.
And now, if you'll excuse me, I have some Doctor Who gifs to reblog on tumblr.