'cept you don't threaten with a ranged weapon...
Of course not, but you can't maintain range forever. Eventually, you'll wind up in melee. Thus, the high dex monk (ideally) takes a position in combat where he can put his AoOs to good use.
My current one is using a polearm (specifically, a Bisento 1d12x2, reach), so I've got a high dex monk with high AC, ranged weapons to soften up opponents (I will hit frequently with either crossbow or javelin), a reach weapon, and IUC to take on those within the polearm's reach. Standing on the second rank, I can usually get in a couple of whacks in before I risk close physical contact, and if they close on me, the Barbarian will get his own AoO.
Once I take Pole Fighter (DCv1) to use the Bisento with FoB, those AoOs will be partnered with a big-ass whirling weapon O doom.
And slightly further down the road, when I take Ring the Golden Bell (DCv1) to be able to deliver Unarmed Strikes (and any attack depending on Unarmed Strike) at range...