[Terribledactyl]

Laptop battery dying isn't catastrophic to the image of the company.

Tesla having bad batteries would be a PR nightmare. Toyota has taken similar measures with their prius, never let the battery go anywhere near a deep discharge. Through over provisioning you can make sure that any given cell is always in its optimal range, and in a big car like a tesla, extra weight wont be that negative. Laptops "need" to be thin and light, so over provisioning the battery means less usable life per charge and/or bulk.