Why would guy flirt with everyone except the girl he likes?

[Anonymous]

I happened to notice that a guy who is outgoing and friendly flirts with other girls but there is a particular girl that he will never flirt. He would talk and treat her differently than other girls. He would always stare at her and smile when he makes eye contact. He would always reassure her when she panic which he would never do to other girls. Why is that?

[Danish87]

Fear of loosing her, and if she is his crush than don't want to have image of that kind of guy so, he want to be like good boy in her eyes.
Every guy has this trait.

[Anonymous]

He's keeping is flirting skills sharp, lol.