Maybe because the Southern secessionists weren't willing to wait, hence all those thefts and war-like actions BEFORE Lincoln even took the oath of office.
If your house is on fire, do you sit in the living room waiting for the Fire Department to confirm the fact the house IS on fire?
South Carolina had already waited 8 years longer than they intended. They were ready to go in 1852.
The people of the State of South Carolina, in Convention assembled, on the 26th day of April, A.D., 1852, declared that the frequent violations of the Constitution of the United States, by the Federal Government, and its encroachments upon the reserved rights of the States, fully justified this State in then withdrawing from the Federal Union; but in deference to the opinions and wishes of the other slaveholding States, she forbore at that time to exercise this right. Since that time, these encroachments have continued to increase, and further forbearance ceases to be a virtue.