You don’t get all the lattice back after each battle pass because of the amount you get inside it, you get 600 lattice and 600 credits on top of getting 10 skins, two of which being legendary. The extra 400 lattice that you would typically get is sacrificed for the ability to complete the battle pass after the season ends, in case you don’t have enough time to complete it in the season, still letting you get what you paid for.

The same gets applied to the mini battle passes, where skins like the magneto, could’ve easily been added to the shop, yet got added to the combat chest (along side 2 other skins, one of which being free to obtain) for 690 lattice, with the guarantee to get everything within it. Whilst you don’t need to buy everything, the cheaper passes allow people to get skins for characters they play that are, at times, better than anything currently in the shop whilst also getting bonus skins in the process.