Direct Questions from NCERT - In Chemistry in the last few years, there are some direct questions that are asked in JEE Mains from nuke and corner of the NCERT Book especially Inorganic Chemistry and Organic Chemistry.
Importance of Some Memorizing Chapters - Some chapters like Environmental Chemistry, Biomolecules, Polymers, Surface Chemistry, Metallurgy, and Chemistry in everyday life may not require any other book or notes.
Base Concepts - NCERT is going to help build some concepts and building blocks that are going to help solve all other types of questions.
Lack of a good amount of problems - There are only a few problems of Physical Chemistry in NCERT to refer through. This makes NCERT not enough for JEE Physical Chemistry.
Lack of some chapters - NCERT does not have some chapters like Quantitative Analysis in them. You should study them separately.