Small shelves can be used for displaying small and delicate ornaments or they can be dozens of feet high holding seemingly endless pallets in a warehouse location. For such a simple object, a shelf truly does appear in a hugely varied number of ways.
Shelves are very simple structures and yet similarly to the wheel, our lives would be very different without them. The ability to store things using vertical space enables us to utilise so much more of the living or work space around us. Even a chaotically organised shelf will enable things to be lifted off the floor for either simple convenience to not be a trip hazard or for practical reasons to make something safer by being out of the way of children or animals for example.
A well organised shelf enables us to access the items we want quickly and conveniently. A book shelf provides quick visibility of the available reading material. A huge warehouse may not facilitate simple item selection through a quick glance but a well organised warehouse with documented storage will enable similarly rapid product selection. The use of automated order picking in robot operated warehouses is only possible through the use of organised shelving. Robot technology may be good but it does not work with uncoordinated clutter, shelving is the route to organised goods storage. It is probably not the case that the shelves populating your own environment are religiously organised to the extent that a robot could find what it needed but, you would surely be lost without the organisation they facilitate.