imagine having a buffoon like Shanks as your rival. The man spend an entire year ragebaiting a random child just for teh lulz. Mihawk giving a shit about the powerlevel of a guy that doesn't take him or anything else seriously reflects pretty poorly on Mihawk's character.
>Ooh look at me, I never smile and I live in a big gothic castle and I've devoted my whole life to the blade and I got this mysterious backstory with the Navy. Now if you'll excuse me I need to take a three week voyage to sword fight a ginger moron before he gets fired from his job of town drunk and has to find somewhere else to pursue his passion for loitering and vagrancy