That has to do with how the shoe fits your foot. We all have different feet. Some shoes will fit your feet better. If a shoe fits one person well, it may not fit the next person the same.
Speaking of shoes that fit oddly, these are my Allen Edmonds Randolph loafers and after wearing them briefly on Wednesday I got such a terrible blister on the top of my foot behind my big toe (odd location!) that I'm considering selling them. Does anyone know how I could try to break them in/remedy this weird fit problem? My right foot was totally fine!