Jesus teaches about prayer like a parent talking about parenting. Would you give your hungry child a snake? Of course not. Even imperfect parents give their children what is good. So, he says, think how much more your Father in heaven wants to give you.
He tells us to keep asking. Not once, but over and over, like a child who keeps coming back to the kitchen. Prayer is not a vending machine, and not every request is granted as we imagine. But nobody who keeps knocking is left standing outside for ever.
And Luke tells us what God most wants to give: the Holy Spirit. We often ask for things, and that is fine. But the deepest answer to prayer is not a thing. It is God himself, living in us, changing us from inside. That is a gift worth knocking for every day.