In my opinion the coaching centers are relevant and useful to students.
There are many students who are brilliant. They may study and perform well on their own. There are many students who are not so good. Their minds are volatile and they need some direction to progress in their studies. Often these students are able to catch up with the subject, if explained in a little more detail or if explained in some other way.
The learning of a person is dependent on the students environment, background and status also. In order to make all students learn in a uniform manner and with the same type atmosphere, the coaching centers will help.
The students who waste their time in activities not useful for their career are better off spending time to learn and reiterate their learning in coaching centers. The staff there tries to clarify some doubts specific to each student. This is perhaps not possible in regular classes. Further, going on a subject lesson a second time, the student's learning is improved.
As long these coaching centers do not become too commercial and exploit students, they are good.