I dunno, super mega white teeth kinda creep me out and it looks fake. Maybe I'm just secretly envious because I'm stuck with these grody coffee stained teeth.
Not everyone looks good with really white teeth. Your tooth color has to match your skin color. I have seen really white teeth on a few that looked awful.
That's not something I've ever cared too much about as long as I know the person is taking care of their teeth. Some people's teeth are just not white, even though they take good care of them. My teeth are fairly white, but they're not perfect. Unless they're particularly bad, I wouldn't judge someone for not having perfect white teeth.
Alas. they dont. They smell very little when young, but with age they get dental problems just like us. If you ever had an elderly beloved dog in the family you will know their breath can be quite foul.
We like signs of health or fertility and find that attractive. There are many natural shades of white people do find attractive. Like JakobA said, though, sometimes darker teeth are a sign of bad hygiene or poor health. Our teeth also darken as they age. Ergo, teeth that are darker- past a normal variant of youthful white- are less attractive to most people.