On Tigers? To spread the weight as much as possible and so prevent the tank from sinking into the ground.
The Germans began using this kind of suspension on their halftracks, then adopted it for the heavier tanks (everything designed after the Pz.Kpfw. IV, basically). Nobody else ever used it, though, because its drawbacks outweigh its advantages: mud builds up between the wheels and can cause them to jam, especially if it’s freezing, and maintenance and repairs are a nightmare: on a Tiger I with the original wheel layout, to access one wheel you need to change, you may have to remove up to
fourteen others. Count them:
View attachment 365343
See which ones you’d need to take off to get at the third wheel from the left on the upper row
By the Tiger II, the Germans had realised this as well and simplified it into two rows of double wheels, which makes maintenance and repairs easier — but you’d still have to take up to five wheels off to get at an inner one.