When people are in a relationship or want to be in a relationship, they tend to do things that are not what they would normally do. Why? Because they want to impress the person they are (or want to be) in relationship with.
That is part of the impression management (or self-presentation) in sociology and social psychology. Basically it is a series of pretending (for being polite) and lies. And that is how every beautiful relationship begins......
* Something I thought about while watching TV show "Common Law"