You can usually relatively straightforwardly divide your monetary resources into a part that you spend on donations and a part that you spend for personal purposes.
By contrast, you don’t usually spend some of your time at work for self-interested purposes and some for altruistic purposes. (That is in principle possible, but uncommon among effective altruists.) Instead you only have one job (which may serve your self-interested and altruistic motives to varying degrees). Therefore, I think that analogies with donations are often a stretch and sometimes misleading (depending on how they’re used).
Can you say why?
You can usually relatively straightforwardly divide your monetary resources into a part that you spend on donations and a part that you spend for personal purposes.
By contrast, you don’t usually spend some of your time at work for self-interested purposes and some for altruistic purposes. (That is in principle possible, but uncommon among effective altruists.) Instead you only have one job (which may serve your self-interested and altruistic motives to varying degrees). Therefore, I think that analogies with donations are often a stretch and sometimes misleading (depending on how they’re used).