Mr Lipwig, chairman of Ankh-Morpork bank, was asked the question when he wanted the paper-money-printing-machines to replace the gold-coin-making-machines in the shortest time possible. Hire more golems, give bonus, do anything possible.
And his answer to the question is:
Because people don’t like change. But make the change fast enough and you go from one type of normal to another.
Do things in a hurry, and it could turn out better for everyone.