The time is so limited, and yet even the inefficient use of time is better than wasting it completely. Using someone else's Anki deck may be a way to overcome akrasia. It could make a difference between starting to learn a topic now or postponing it to unspecified "later".

This said, I personally prefer making my own cards. On the other hand, it is probably not efficient. I just enjoy the feeling of control over the deck. I could probably get the same level of control more efficiently by starting with someone else's deck and then editing anything I don't agree with.