Psalm 50

Why does God request sacrifices from his people? That seems to be the unspoken question that God seeks to answer through the psalmist. God doesn't need food. He doesn't want an animal killed so that he can enjoy the bloodletting. God asks for his people to sacrifice so that he can view the heart. Is the heart of the one giving filled with joy at the opportunity to give? Are the words spoken in the heart "thank you"? The sacrifice may not be a reflection of the heart of the worshipper, but in that sacrifice God sees the depths of the person. Then he can judge them; the righteous for salvation and the wicked for judgment.
It took me about 2 minutes to read this psalm.
Stuart