Well, if you are lazy to run around your BH to set up for this kind of shot.
Remember, you can hit an insideout FH when the ball is a bit short and you have the time to run around it, the rest is like you are hitting your regular FH just that your target is the backhand of the RH opponent. Instead of hitting your FH in a deuce corner, you are hitting it in the ad court. It's an aggresive shot if hit properly.
Go to www.tennisplayer.net
and watch Federer does that.