Because it makes him look badass (not that he generally doesn't look badass but it makes him look even more badass) and it shows his gorgeous skin and muscles more than the European clothes, and I have a bit of a kink for people who aren't bothered by wearing less than the people around them, especially if it's a perfectly innocent "where I was raised this is a perfectly appropriate thing" thing. And he looks more comfortable/confident in it, and that's sexy.
So I want The Outfit to get appreciated by someone, anything from looking, through looking and fantasizing, innocent compliments, not-so innocent flirtirting up to straight-up partially clothed passionately vigorous sex.
TLDR: Connor looks good in the ToKW outfit. Someone (Aveline? She's not in ToKW but she could probably appreciate a nice, gorgeous guy) notices he looks good.
No creepiness or noncon please.