Just look at it as wear and tear. Doesn’t matter how miniscule it may be it’s still eating up your storage and battery life in addition to battery charge. Sure you could charge at work too for battery charge but as miniscule as it is it’s still killing your battery life.
Also, don’t give corporations any leeway because they WILL take advantage of the employee given the chance. For every single rule and regulation that helps the employee someone had to spill blood to achieve it.