jimclarke:
That is strictly the case in many places around the world, and there is often a good reason for it.
If you are diving a place (like Cozumel) that has strong currents and the standard procedure is drift diving and dive flags are not possible, then the boat cannot have every pair doing their own individual pre-planned profiles. If you are drift diving with surface flags (as in the Fort Lauderdale area), it is no problem for the boat to keep track of everyone; withiout those flags, it is important for people to stay in a group.
In other cases, a DM in the water is essential to find a target site. Try to find the Devil's throat (Cozumel) entrance without a guide. In Yap, our guide himself missed the opening for Yap Caverns--we would not have had any chance on our own. In Truk Lagoon, the guides provide you the opportunity to explore regions of the wrecks you would never find on your own, or never get out of if you did.
In these cases, you are indeed surrendering some of the planning responsibility to your guide, and I do it in those circumstances without hesitation. You should not put yourself totally in the hands of your guide, though. You should know before committing to the water what kind of a profile you are capable of doing with the surface interval you have had, and you should be ready and willing to overrule a DM who is leading you astray--and I have done so on several occasions. You also have more control over the planning than you might think. For example, in Truk Lagoon recently, my buddy and I discussed with a guide what we wanted to see when we wanted to get into the more challenging areas of a wreck, but we also told him when we planned to go in, based upon our own analysis of the surface interval we needed since the previous dive.
