What is the major advantage of randomised sample in a clinical trial?

Randomization is a statistical procedure by which the selection bias is reduced and thus the paicipants are allocated into study and control groups. By randomization, there is equal distribution of factors between the two groups and thus comparison is allowed. Although randomization makes the groups comparable, it does not 'ensure' comparability. Ref: Park's Textbook of Preventive and Social Medicine, 19th Edition; Pages 77 - 78