Why Is the Author of the Psalms Always Quoting Tora?

The author of the letter to the hebrews almost always talking about tora, but almost never quotes tora. So so they're reading the penatuch through the lens of the psalms, rather than always going right back to the penateuch. In some cases are clearer than others. But we still have to see these later receptor texts in the old testament still might be pulling their thoughts when they go back to the original donor text.