Explanation:
Starch is a high molecular compound, and its hydrolysis is slow. In order to save time and ensure that it will not deteriorate under the long-term action of air or bacteria, it is best to heat it to speed up the hydrolysis (please ignore this sentence if you are willing to wait for dozens of hours);
Maltose is disaccharide, which can be directly obtained by condensation of two molecules of monosaccharide, and hydrolysis is only until one molecule of maltose is hydrolyzed to obtain two molecules of glucose, so it is fast enough without heating (although it is not instantaneous, it is at least much faster than starch), and of course heating can accelerate hydrolysis (but it is not necessary).