Question

Why electrons alone flow in electric current

Answer 1

Because protons are in the nucleus
And electrons will revolve around the nucleus
So it pass

Answer 2

 Protons have a charge and indeed the flow of protons would constitute electrical current. Neutrons have mass but no electrical charge and cannot constitute electricity. Electrons flow from negative to positive yet it is taught that conventional current flows from positive to negative.  
That is an erroneous assumption.

so' thats why electron alone flow in electric current