Because he’s an actor who, nebbishy and non-threatening though he may be, often plays the romantic lead and thus has a lucrative career that depends to some degree on being viewed as a sexual being. Basically, the same reason that if Taylor Lautner or Justin Bieber were gay (which to my limited knowledge neither is) it wouldn’t be a great idea to own up to it just yet as their earning potential might be damaged. (I’m not advocating the closet but the “I don’t discuss my private life” route.)
I question this basic premise. Who views Michael Cera as a sexual being, even in a limited way? I’ve never heard anybody express any sort of sexual desire for him or attraction to him, and I wonder if people would like him more as an actor if he did have any sort of sexual energy.
He was interviewed in a recent issue of Rolling Stone and his sex life came up. He admited to losing his virginity around 17 and stated he’s had a pretty steady, if uneventful, sex life ever since.
I’ve heard the gay rumors about Ellen Page much more than Michael Cera, but I think for both it comes to the fact that they’re young, considered an It Girl/It Boy and have no noticeable social life. That confuses the gossiphounds who expect every actor to be drinking and whoring it up all the time.
In that same Rolling Stone interview, he relates a story where a female fan comes up to him and squeals “Oh my god! You’re Michael Cera!” He says yeah, yeah, and then she asks “Can I suck your dick?”
I don’t think that’s an uncommon occurence for any actor.