Starting the day with a warm-up is a means of connecting you to your instrument mentally, emotionally and physically. It is just not a physical thing. Rehearsals and coachings also need a warm-up or tuning time, (which is just not about pitch!) so people can acclimate to the environment that is generated by everyone in that rehearsal. That atmosphere can be so dispersed because by majority people come in unfocused to the task. They are offset to what the task calls for. Warming-up the individual and the group is vital to be able to work together in shared purpose.
On another note, it takes so much more effort of the 'right' kind to accomplish something at a higher standard than what most students are aware of. I feel my job as a coach and teacher is to help bring awareness to that point. Air-support is one great example. AIR-SUPPORT MEANS ACTIVELY ENGAGING SOMETHING WHICH IS INVOLUNTARY INTO A VOLUNTARY DELIBERATE ACTION. (Breathing is involuntary and brass playing is voluntary). That takes EFFORT. Effort of the right kind. This can only come through practice, meaning constant, regular, thoughtful, attentive work. Even when we have some accomplishment and our efforts are closer to the 'right' kind, (meaning our automatic systems are filled mostly with habits that are efficient, and balanced in their mechanics), we still can't totally go to sleep at the wheel. This is another great thing about warming-up, it keeps us 'tuned' so to speak to what we are doing. If warming -up is regular, we can tell when things need adjustment.
It seems at times because of all there is to learn, retain and juggle, students can loose track of what they are aiming for. When I am coaching my groups, I always try to assess afterwards if I was too demanding. My focus is on what it takes to get the musical results, which does in my mind, automatically include the basics of ensemble playing. But each person has to be at full and that is where oftentimes the efforts fall short. If the standards in the practice room were higher, then maybe the attitude of finer standards would appear in the ensemble playing as well. Because focus and holding to the standard would have been 'practiced.' The greater efforts would be a regular feature.