This has been asked and answered many times. DSB was specifically designed to give you a way of making belts much more powerful by increasing their throughput without changing inventory "density". DSB, and the earlier Deadlock's Crating mod, were the first packing/stacking mods for Factorio that did this and also aligned processing times with belt speeds. There were already packing and crating mods around at that time (0.15? 0.16? I don't remember) that compressed items in the way you are talking about. I wanted something different.
However there are other mods that change this balance in DSB, for example the Deadlock Experimental Stacking mod. There are also many, many mods that change inventory storage sizes or stack sizes generally. Search the mod portal.