why is it important to walter that travis looks uo to him?

It becomes clearer that Walter's impulses are primarily class-motivated...Part of Walter's oppression is his emasculation. His subservient job as a chauffeur and his inability to provide adequately for his family all whittle away at his self-esteem. WAlter wants his son to see him in a different light. He wants Travis to see him not as a servant of rich white people but as a black man who has forged his own destiny.

It's important to every man that his son look up to him. Walter just wants what every man wants, and he doesn't have it. He wants to be able to give his son whatever the boy wants in terms of education and opportunity. He wants to feel rich for just a moment, so he gives Travis his carfare. He wants Travis to view him as someone he wants to be like when he grows up.