Whether one should seek coaching or not is an individual choice. Several Civil Services aspirants have cracked the Civil Services Examination without taking any coaching. It was possible because of their confidence, self-motivation, determination and persistence. If one has a track record of accomplishment without much external support, one can try without any coaching.
But why do an overwhelming majority of students join? There are advantages, quite obviously. Experienced and senior faculty can cut your learning curve short. Save your time from heaps of information which students generally read but without any exam value. Get to systematically learn all subjects within General Studies: many being technical, need guidance. Trend spotting is another benefit. You also get to meet likeminded people, understand their perspectives, take tips from their learning styles, improve your knowledge and remain abreast with latest updates. The competitive environment keeps up your motivation levels. Taking Tests that we conduct regularly will help you improve your speed and ability to handle different types of questions. You come to know where you figure.