Why can't people handle anyone who isn't always happy, bubbly, cheery, etc?

I don't know if it's just around me, or what, but it's very annoying. I haven't met one person who can handle my personality. And I'm not expecting most people to, not at all; I'm very cynical, sarcastic, pessimistic, harsh, etc. That's just how I naturally am. So far, nobody has ever been able to handle it, so I hold back and don't really say much at all, I'm actually quite quiet now. If I do start to talk a lot, my family (don't have many friends because I'm not, as mentioned, overly happy and bubbly) give me freaking hell for whatever I say. I feel like I have to act like someone I'm not if I talk, because they can't accept the way I think. My mom in particular. She doesn't want to hear anything that isn't superficial and happy, she doesn't like to think anything deeper than the latest lady gaga song. If I say /anything/ that doesn't sound like it came out of some naive, perfect little girl's mouth, she tells me to shut up and quit being too 'depressing,' 'cynical,' whatever. I was already quiet to begin with, now I barely ever talk and everyone wonders why.