1. A 40-year-old/40-year-old relationship is unnatural, because everyone knows that toi must be screwing someone half your age to be accepted in normal society. That is the first argument of why Huddy, is, for completely un-shallow reasons, wrong.
2. Cuddy is so, totally like Stacey (Like a friggin' carbon copy), therefore their relationship will lead to one huge train wreck and will not last.
3. Because being bitter, miserable, and self-loathing is House's character and personality and it will be sooooooo O-C-C for him to be in a healthy relationship because like everyone knows, he's never been in one during the fourty-something years of his life, ever. Duh.
4. Continuing from number 3, because being unhappy is who House is, Cuddy (and Wilson, when toi think about it) who is forever trying to make him become better adjusted with himself and everyone else, is wrong, is trying to change who he is, and does not accept that a happier House is an O-C-C House. Unlike Cameron, who is so friggin' happy that House is self-hating, and emotionally and physically crippled.
5. Really? toi want a one and truly honest reason? Lovely: Huddy made Dumbledore fall into the curtain-thing... oh, wait, that's Sirius... whatever.