In general, having weird beliefs and politics makes it very dangerous to speak on live TV. Interviewers and editors are incentivized to make you seem crazy, scary, or ridiculous depending on where you appear. Eliezer is especially leery (justifiably so given his experiences with journalists) of this sort of thing, and he's the most prominent LW public intellectual.

There's also a question of need: Given that Elon Musk knows about and has given millions of dollars to the cause of AI risk, does MIRI really need to do TV publicity?