Why is it important for scientsts to use the scientific method?
Because it helps prevent you from thinking things what ain't so.
See this old answer. Anyone can make a mistake, can make an error of fact or interpretation; the scientific method is a way of minimizing these mistakes. An experiment is performed, and the results allow the experimenter to shoot his mouth off. Suspicious of these results, other experimenters (i.e competitors and colleagues) try to replicate the results; some of them MAY be able to find the error in the original experimenter's reasoning or in the particular experiment.
Alternatively, the other scientists may be able to replicate the results of the original experiment, and a new example of experimentation may be developed.