During the Har Sinai revelation, God spoke to the nation only the Ten Commandments. He could, for example, give a very different speech, for example, include theology, as He did with Job (38.1):
"Where were you when I laid the earth’s foundations?
Speak if you have understanding.
Do you know who fixed its dimensions
Or who measured it with a line?
Onto what were its bases sunk? ... Have you ever commanded the day to break,
Assigned the dawn its place,
So that it seizes the corners of the earth And shakes the wicked out of it? ... Have you surveyed the expanses of the earth? If you know of these—tell Me."
maybe discuss cosmology, or repeat the words He said to Moses (Ex 19.3):
"You have seen what I did to the Egyptians, how I bore you on eagles’ wings and brought you to Me.
Now then, if you will obey Me faithfully and keep My covenant, you shall be My treasured possession among all the peoples. Indeed, all the earth is Mine, but you shall be to Me a kingdom of priests and a holy nation.”
Another option that comes to mind is the blessings, as in Lev 26.3, I bet Israel would love to hear those promises from God's mouth:
"If you follow My laws and faithfully observe My commandments, I will grant your rains in their season, so that the earth shall yield its produce and the trees of the field their fruit. Your threshing shall overtake the vintage, and your vintage shall overtake the sowing; you shall eat your fill of bread and dwell securely in your land. I will grant peace in the land, and you shall lie down untroubled by anyone; I will give the land respite from vicious beasts, and no sword shall cross your land. [Your army] shall give chase to your enemies, and they shall fall before you by the sword."
But God chose to dedicate this once-in-history event to relaying the Ten Commandments that, weirdly enough, have no particular importance in Judaism.
Hence my question: why did God's revelation on Har Sinai only include commandments (given that "I'm YHWH thy God" is the first one)?