Wizard.WizardSteps not in ViewState

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In some case, I remove some WizardSteps form a Wizard.
I put the remove code in Page_Load:

protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
Wizard1.WizardSteps.Remove(aStep3);
Wizard1.WizardSteps.Remove(aStep4);
}
}

But I found when post back, the removed WizardStep appear again.

Why, Dose not the Wizard reserve it's state in ViewSate?