Imperative will sound different when used between people who already know each other and those who do not know each other.
When a person is invited to a TV channel to speak, they know that they will be expected to tell the audience something. Any formulas of politeness have already been exchanged behind the scenes. It's not like the interviewer just approached a person on the street and asked, "Tell me about X." Guests on talk shows or news shows come there after a lot of back-and-forth between the producer (or the anchor) of the show or their staff and the guest and/or his/her staff.
Since air time is scarce (and expensive), no one will waste it on formulas which have already been exchanged before. The goal of TV shows is to keep the viewers' attention. That's why everything that is said is as much to the point as humanly possible. No one will watch small talk; viewers will simply pick up the remote and switch channels if they are not being given something that is pertinent and interesting.
Even when you see street interviews, you can safely assume that the journalist first approached the person and politely said something like, "Good day, would you mind if we asked you a couple of questions about X." (I have once been approached this way at the polling station on election day; and the journalist was very polite—but the camera was off until I said, "Yes of course.")
Since the time of TV shows is usually limited, all of this preliminary politeness simply gets cut from the final version of the program that you see on your TV screen.
Another (albeit minor) difference is that "Give me the pen" is a claim on someone's property—and no one gives away his/her property just so; while asking someone for their opinion is asking for something that people are only glad to provide.