Head Gasket Preference

Guys, I have noticed that it seems like the Fel Pro 1008 is the "go-to" head gasket for small block Mopar with .039" compressed thickness, and a 4.180" bore. What is the science behind using a gasket with a bore much larger than the bore of the engine itself. I noticed that there are Cometic gaskets available with 4.040" bore, and 4.060" bore. When would a gasket with a bore closer to the cylinder bore size be ideal? Thank you for any responses, I still have a lot to learn.