If you a) had a time machine and b) chose to go back to Missouri circa 1820 instead of chilling at a Roman feast, you'd probably hear the following sentiment:

What's the point in being a part of the U.S. if the Feds are just going to cram down their own laws down your throat?

The Missouri Compromise is, above all else, concerned with the rights of self-determination. The U.S. was founded on this ideal as much as on any other, and so it would have been pretty hypocritical of Congress to reject Missouri's desire to draft its own constitution.

Of course, the government wasn't just going to up and hand this over without getting something in return. Politicians are big believers in tit for tat, quid pro quo, and you-scratch-my-back-and-I'll-scratch-yours.

This right of self-determination was held in check by the explicitly stated need for Congressional approval, like this one:

And be it further enacted, That in case a constitution and state government shall be formed for the people of the said territory of Missouri, the said convention or representatives, as soon thereafter as may be, shall cause a true and attested copy of such constitution or frame of state government, as shall be formed or provided, to be transmitted to Congress. (7.1)

Basically, the Missouri Compromise is saying, "Oh, you want a constitution? Have at it…but you don't get to keep it if we don't like it." After all, Congress couldn't have state constitutions just up and contradicting the Federal government's fundamental right to set the laws of the land. Why, that might even lead to civil war.

Unlike this whole Missouri Compromise thing, right? Right?