And when the disciples saw it, they were indignant, saying “Why this waste? For this could have been sold for a large sum and given to the poor.” Matthew 26:8
I didn't realize the the disciples were so practical. In this scene a woman is pouring our expensive essential oils [sorry] on Jesus to honor him. Where she got it, we don't know, but we do know what the disciples thought of it: they thought she was wasteful. "It could go to a better purpose like...I don't know...the poor!" They were angry which, for some reason, surprises me.
To them it seemed like a waste, but to Jesus it was good, meaningful, appropriate. The ointment would have a practical purpose (to prepare Jesus for his burial) but, it had time to wear off. That must mean that the practical wasn't the main point.
The heart of the matter was the heart of the woman: she loved Jesus and would "waste" what was valuable to her to honor him.
For similar reasons we pray. We pray when we could act "practically" instead of waiting patiently ("This could have been sold...and given to the poor"). We pray when it seems like a waste of time, spiritual resources, and heart.
We pray because Jesus is worth "wasting" our effort on. He is honored when we pour ourselves out. He is pleased when we are bold enough to try.