Why does he say I deserve someone better?

When someone says something like, “You deserve someone better” or “It’s not you, it’s me” that is code for the idea that they want to break up with you.

Also people will often say they have been hurt in the past, as a way of creating a self-fulfilling prophecy that they will have to break up (with you) so they don’t get hurt again.

I don’t really buy it though. If they didn’t want to get hurt, and they picked someone decent, and they are truly interested in having a relationship, then they would be in a relationship and work to make it good.

I think people often use the “I’m afraid to be hurt” excuse to avoid intimacy, and to play the field with a variety of people.

Maybe he means that it is “HE” that deserves someone better?
He is projecting his doubts onto you and others.
Leave him as he is playing mind games with you as if you are supposed to follow a dialogue
of” Oh no you are so…fantastic etc” and end up uplifting him.
Its all for his ego. Some play the victim for you and others to pamper him.
I guess it all depends on the ages of the people involved? If young then he has to learn better ways of inciting girls/women than mind games. He sounds immature and has pegged you as his next victim to support his damaged ( if true) ego.
Keep your distance and don’t fall into the trap of always uplifting him, you are not his counselor,nor mother.