That's a good question

She's still wearing more clothes than you are, Caenis.

Plausible in lore answer -
Sex appeal makes opponents lower their guard?

Real world answer -
Sex appeal makes people lower their guard on their wallets?

Zekana said:

Plausible in lore answer -
Sex appeal makes opponents lower their guard?

Real world answer -
Sex appeal makes people lower their guard on their wallets?

Considering this is Nero in Fate, just sex appeal.

Nero just being an attention whore, that's probably it

FJH said:

She's still wearing more clothes than you are, Caenis.

It is both sad and hilarious that that is true.