There are many reasons our prayers may lack power. Sometimes they become routine. Our prayers become hollow when we say similar words in similar ways over and over so often that the words become more of a recitation than a communication.
We are all busy. It's easy to find excuses for not reaching out to others, but I imagine they will sound as hollow to our Heavenly Father as the elementary school boy who gave his teacher a note asking that he be excused from school March 30th through the 34th.