The thing people need to realise and understand is that Harry is himself an innocent teenage boy, needless to say an orphaned boy. He hardly had money to his name before he came to know about the magical world through Hagrid after his 11th birthday. An innocent orphaned kid like him can't possibly think of giving it away just like that at that age even to his bestie. When Ron broke his wand it was an accident in their second year starting, as they reach their school in Weasley's flying car and get hit by the whomping willow. The incidents that followed that year what with the chamber of secrets getting opened, literally makes Harry forget about his best friend's broken wand issues. Then as the third year starts Weasleys win an Egypt tour and prize money with which Ron's parents themselves by a new wand. When Ron feels horrible about the Dress robes his mother gets for the Yule ball that's one instance where Harry really feels horrible for his poverty. Still he knows Weasleys would never accept the money he inherited from his parents like charity especially since he didn't have a living parent of his who could look after his monetary needs. So when an opportunity of extra money comes in his hands, that's when Harry decides that he doesn't want that for himself and he donates it entirely to the Weasley twins knowing they need it for their business capital amount. From that he makes only one request, which is for his bestie Ron, to get him some decent robes as he saw how much the old robes made Ron a laughing stock among the school kids. The scenario before this never was quite right and it wasn't his place to give money to his friend just because he has it and Ron doesn't. But when the time comes for some extra money which he didn't actually need, he gives it away and has Ron's need first in mind. That's how Harry is.