Philly steak rolls

Steak/hoagie rolls, but “philly” seems to be a term most people can understand.
Anyway, I usually use KABF but i have read some places who make their own rolls use a mix of either a bread flour, or a high gluten, and 00 flour. I have no problem experimenting, but can someone explain the benefit of using a the mix? Is it a protein reason, or something else? Because why not just adjust a low protein flour and add a high protein flour. Or vital wheat gluten for that matter? If its not a protein reason, is it a texture reason? If so, what does 00 bring to the table in terms of texture?