Many times in my life, I came across people who would keep asking me for favours. For the first and second time, I happily gave them what they wanted. However, if they kept on asking, I tried to hide from them so that they don't ask me again. I believe, all humans do the same. Even a mother gets irritated at the child if he/she keeps on asking her for things again and again.
On the other hand, the more we ask Allah, the more pleased He gets. Such is Allah, the most Merciful. We should all learn the ways to ask Allah for anything we need.