Perhaps for lower level horses changes and lateral work are not appropriate, but for higher level horses these things are absolutely useful parts of warming up and they provide the kind of physical and mental activity that prepares the horse for harder work later. Like I said above, people forget that these things *create* suppleness, they are not just something you do once suppleness is already present.
I do not agree that a horse should be over its back, connected and in front of the aids after only walking or that such a thing has to do with training of the horse or skill of the rider. Walking alone does not allow horses to stretch in a way that most need for those things to happen in a very truly meaningful way. Horses may feel more or less round right out of the gates and a horse can certain be on the bit and responsive, but true connection and roundness and even real, enthusiastic bit contact do not typically happen after just a walk and if that is your goal I think you are likely to be disappointed.
And there can be many factors influencing these things aside from training - it could be the weather, turnout time, diet, tack, teeth, small injuries, etc. Perhaps he is simply bored and needs a lot of stimulation. Or he needs relaxation. It may depend on the day. Finding out what is causing the problem is a good way of resolving it. And I'm not quite sure what you mean about "letting [your] horse piddle around" - warming up is not piddling around, it is doing the very things that will fix crookedness, tension, and resistance.
Last edited by plomme; 03-18-2013 at 10:22 AM.