Many missed approach procedures contain instructions such as "climbing right turn to xxx degrees". An early turn could conflict with terrain (think RNO landing south). Therefore you are required to continue to the MAP prior to starting any turns, even though you may have decided earlier, such as at the VDP, that you will not be landing out of this approach. There are also some rare approaches that have maximum altitudes on them for crossing traffic at another airport(OAK landing east crosses under SFO landing south), and some where the missed approach has a final altitude that is below the outer marker crossing altitude. So in case of an early missed approach decision you can't always start an immediate climb, and in the case of ATC speed restrictions you may not even be able to accelerate to your flap retract speeds. You will of course request relief immediately from ATC, but it is simetimes hard to get a word in edgewise, and when you catch him by surprise his response is likely to be "fly the published miss". I know that some people will say that this clearance removes the speed restriction, but since the speed restriction may have been for seperation with the traffic ahead, speeding up may create a traffic conflict.

Joe