what's the main use of exceptional handling?

Answer 1

If you don't handle exceptions, the users of your program will find it disappointing to see
code lines explaining the problem to them which they themselves wouldn't still understand.
As a programmer, you have to make your environment user friendly by handling all possible
exceptions.

Answer 2

If you don't handle exceptions, your program crashes when encountering one. Handling exceptions allows you to indicate what the program should do instead.