Actually notBecause I guess it's awkward to call her by her name in Japanese culture?
Because it's easier to say "wife" than Sakura?
Because why not?
Sasuke uses "tsuma" which is rarely used by Japanese men to their wives (some are embarrassed to call their wife as that) compared to the other common terms that means in the back
Tsuma is the word for wife and used as equal to him unlike the other common terms.