Oh but yes they do care, my best example is riding my JD gator . If you keep moving ,no matter how slow deer stand and watch but the instant you stop they are gone in a heart beat.
I believe there is day and night difference in how you spook a buck. If your hiding and he winds you before he sees or hears you ,he will be spooked. If you are bumbling along walking a dog and give him warning that you are there chances are he will lye low and let you pass him undetected.