Technically, Reformed Theology does not exclude liberty from sovereignty. Quoting from The Westminster Confession of Faith, Chapter III, point I:
I. God from all eternity, did, by the most wise and holy counsel of His own will, freely, and unchangeably ordain whatsoever comes to pass; yet so, as thereby neither is God the author of sin, nor is violence offered to the will of the creatures; nor is the liberty or contingency of second causes taken away, but rather established.
Calvinists define free will as the freedom to act according to one's nature. From a Reformed perspective, including a truly random perturbation to provide a certain kind of freedom would not increase the power of the individual's will — the perturbation would be just as external as a Divine decree — but rather establish a lesser but coworking god called Chance to which (in some small part) creation would be subject.
Similarly, God accidentally getting creation just a little wrong so that unintended consequences occur would not increase the freedom of the individual, but such would indicate an imperfection in God. Such a concept of a fallible God is offensive to many Christians.
In his letter to the Romans, Paul provides a response to one complaint about such sovereignty. (This response seems similar to what God told Job — effectively, 'I am God and you are not'.)
One of you will say to me: "Then why does God still blame us? For who resists his will?" But who are you, O man, to talk back to God? "Shall what is formed say to him who formed it, 'Why did you make me like this?'" Does not the potter have the right to make out of the same lump of clay some pottery for noble purposes and some for common use? (Romans 8:19-21 [NIV])
The writers of The Westminster Confession of faith closed Chapter III with a recognition that such is a difficult teaching and with a declaration that this teaching is not an encouragement to passivity but rather toward worship and obedience (and peace/assurance):
VIII. The doctrine of this high mystery of predestination is to be handled with special prudence and care, that men, attending the will of God revealed in His Word, and yielding obedience thereunto, may, from the certainty of their effectual vocation, be assured of their eternal election. So shall this doctrine afford matter of praise, reverence, and admiration of God; and of humility, diligence, and abundant consolation to all that sincerely obey the Gospel.