Setting them as high as possible is not the same as 'adjusting them evert time I use them.' I set mine as high as possible too, but if they were always the max height and not adjustable it wouldn't make a difference.
You don't have enough room under the car to put the jack stand under without jacking it up. You jack up the car then transfer it it the stand. I thought the pictures were easy to follow...
The top of the jackstand detaches and sits on the top of your jack. These have special slots, pads, or locator pins, depending on what your car came with from the factory. You jack the car up, slide the stand around the jack and let the jack down. Now the pad that was on your jack is supported by the coller of the jack stand with a very quick, seamless transfer from the jack to the stand, and you car is supported more safely on a spot designed by the factory, with the correct attachment.