Kingdom of Priests

I find it fascinating that God said this before he gave the law: "Now if you obey me fully and keep my covenant, then out of all nations you will be my treasured possession. Although the whole earth is mine, you will be for me a kingdom of priests and a holy nation" (19:5-6). Verse 22 says, "even the priests, who approach the LORD, must consecrate themselves, or the LORD will break out against them." This is the first time in Scripture that priests are mentioned (besides "Melchizedek" and the "priests" in Egypt). This is before the tabernacle and before the temple. God's plan has always been that we would be priests. He wants a face-to-face relationship with us. Why do we turn away? Why do we try to earn our way or make another way to him?