Apple Pay doesn’t have the support of the banks in India and current banking regulations do not permit Apple Pay to work there.
Apple Pay uses different technology than Google Pay and similar payment systems. Apple Pay uses a Digital Device Number while Google Pay uses a less secure host card emulation process. Google gathers more of your personal information.
Apple Pay uses biometrics (no PIN) which current Indian banking regulations do not permit. Lastly, the storage of the data differs between the different systems with Apple Pay using anonymous information that can’t be tied to the individual.