“You know you’re pretty”. Why do guys say that to girls?

Anonymous
Does it imply the girl presents as full of herself or arrogant? A couple guys I’ve dated or been interested in, instead of complimenting me normally like “I like how you look today” or whatever, they’ll say “you already know you’re beaut” or something. I’m worried I come off as narcissistic? I make an effort to be modest about everything.
“You know you’re pretty”. Why do guys say that to girls?
1 Opinion