The band of stability curves upward at higher atomic numbers, why?

Since neutrons have no charge, excess protons are required to keep the nucleus of an atom from falling apart.

To keep a higher number of electrons stable in their orbits around the nucleus, a higher nuclear mass is required.

As the atomic number increases, nuclear repulsions increase. Therefore, excess neutrons are required to reduce intranuclear repulsions.

Excess neutrons are required so that they could be converted to protons in needed.