A full charge to 100% takes longer. Fast charging is more intensive on the battery - you don't want it to be running on fast charge the whole time. It's for s

A full charge to 100% takes longer. Fast charging is more intensive on the battery - you don't want it to be running on fast charge the whole time. It's for scenarios where you might forget to charge or it's been sitting unused for a while but you still want to get to work quickly. It minimizes failure scenarios. It's meant to be a wireless mouse. Emphasis on wireless.